Brent: my set of completely original (greasy and grimy) VC's like that, have no stickers. I can't remember which engine/car they  are from. But certainly not a 428.
Cleandan: is that what an original air cleaner element looks like? Is that an original style air cleaner?
Richard

If your engine was equipped with the "low restriction" air filter housing the air filter looked very much like the one shown in the photo.
A somewhat creamy yellow, pleated element, orange foam encasing the ends, and a metal cage around the pleated element with circular holes.

The air filter top and bottom changed for 1966 and there were two versions of the same open element filter housing.
Chrome: Part of the engine dress up kit. This would have a chrome top with an engine blue bottom.
Standard" This would have both parts painted engine blue, otherwise the parts were the same between the chrome and painted versions.

If you look at places like Scott Drake, Summit, and others the chrome 14" filter housing they offer is usually the same basic design as the 1966 version...just crappier chrome and metal than originals, but often less rust than originals too.

Good day Brent. This appears to be a Galaxie 7-LITRE engine compartment, is this correct?
I have had mine for decades...still a POS, but I like it anyway.
When I got it things were very untouched...worn out, but untouched.

The round sticker was centered on the oil breather/fill cover top.
The air cleaner lid sticker was on the outer rim, flat area. Not on the inner portion like in the photo.
The service sticker was on the drivers fender well, on the outer side of the fuel hose, near the plastic clamp, about 1/2 way between being next to the clamp and the top of the inner fender curve, positioned as to be read from the front of the car, not sideways as if standing with your body against the front fender. But not perfectly aligned either. I was stuck in the general area with some care, but not critical care.
There should also be a round sticker, centered, on the brake master cylinder cover.

This photos I see the air filter lid wing nut is so tight it has bent the lid. For 1966 the lid top is flat, not curved, with a slight recess for the wing nut.
I see other things too but I'll leave that go.

I tried the Lock Right locker, from Powertrax, in my 1990 F250. This is my daily driver with a stock 7.3L IDI diesel and 3.73:1 gears. I figured with my marshmallow diesel, and ho-hum driving style, the Lock Right would be a perfect fit for my traction needs.

First, Powertrax was really good about helping me get this right. I eventually spoke with their in house engineer a bunch of times and I did all kinds of measurements, fittments, and so on in an attempt to get things just right. Everything measured correct.

In the end I tried two different Lock Right lockers, as well as measuring and combining parts from all of them, to get the best fitting, most correctly measured set up.........And it still would not work properly.
I got really good at taking the thing in and out, so I got that going for me.

Finally the engineer admitted that some differentials just don't work well with the Lock Right and my Sterling 10.25" was one of them.

The problem was it acted like a spool, with ZERO differential action, and this made the truck drive...well, not properly.

I think the Lock Right can be a good alternative for getting better traction, and they seem to hold up pretty well based on what other people have experienced, but they are a lesser locker than other alternatives.

I eventually installed a Yukon Grizzly Locker (a more durable Detroit Locker) and have been very pleased with the set up for the last 70,000 miles.

I didn't try to boil race gas, but it solved the problem I was having.  I eventually went to a return style fuel system on the car, and re-routed the fuel lines to keep them away from the engine as much as possible, and that solved the problem.  FYI the fuel was 92 octane with 10% ethanol.  Race gas would certainly boil at a much higher temperature.

New cars don't need to worry too much about the boiling point of the fuel, because with direct port injection used on new vehicles, the fuel is under pressure right up to the point where it is injected into the engine.  45+ pounds of pressure raises the boiling point significantly.  The problem I was having was a heat soak issue; I would stop the car, the fuel lines would get hot as the underhood temperature went up, then when I started the engine again after about 20 seconds the hot fuel would go through the needle and seat, lose pressure from the fuel system, boil, and spit out the carb vents, flooding the engine.  Took me a while to figure it out, it seemed like the engine was fuel starved, not flooded, but finally one day I duplicated the conditions while the car was sitting in the driveway, and watched it happen.  The amount of fuel spitting into the carb was rather remarkable...

This sounds like a great job for a GoPro camera in the engine compartment.
I know the fuel is evaporating due to heat soak, and boiling when the engine is shut off because the fuel pressure drops...This is plain science at work and there is not much I can do about it.

I never thought about the fuel boiling so violently that it would erupt out the vent tubes.
Currently I have the floats adjusted so the fuel is just barely at the bottom of the view port threads when slightly shaking the car to check levels.

I wonder if lowering the level a bit more may help. I will know, due to fuel starvation and the engine losing power, if I get the level too low.

Thanks for the reply's so far. I have been mulling over all the ideas given already.
1) Yes, one possible gas smell could be coming from the fuel tank vent itself. The tank vents under the Cobra but pretty much behind the seats. With the way the wind flows over this car it could be pulling in the smell.
If anyone knows how to verify the gas tank vents is working properly on an ERA Cobra I would like to know.
Who knows, maybe there is a check valve in there that failed...I am not certain other than I see a tube that is not leaking that I know is the vent.

2) The camshaft is a Comp Cams 282S...not too radical in a .030" overbore 427. Edelbrock aluminum heads with lash set cold a .016"

3) Vacuum at idle is about 11-12"hg. It is pretty good and steady with the slightest of gauge needle flutter. (I'm using a 4" diameter gauge)

4) I smell the gas most during hard acceleration, after shut off (vaporizing in bowls I suspect) and sitting at idle like a stop sign. There is a wiff here and there when driving and I am aware I may be hyper searching for the gas smell at this time too...But it is stronger than other dual quad 427's I have driven and worked on.

I am using BP 93 octane pump premium. I could fill up with 100LL av-gas and see if there is a difference. I know the new gas formulas are NOT carb friendly for a bunch of reasons, lower vapor pressure being one of them.

5) I am aware of the vents to atmosphere of Holley carbs and understand the normal smell of engines with these carbs are becoming distant memories, rather than daily occurrences. Pretty much any carbed vehicle will smell some when partked after a full temp drive, but this one is quite a lot more.

The carbs have Ford part numbers so I assume they are Ford original Holleys, not reproductions.

Thanks again.
No ideas are bad at this point...well, maybe the riding naked with a porcupine in your lap idea is a bit sketchy...otherwise they trigger ideas that may get me to a good end.

With a V-Belt, the tensioner does not work well like it does with a poly-V belt.
If you use a tensioner with V-Belts you should run the pulley on the V side of the belt.
If you run the tensioner on the back side of a V-Belt it tends to break the back of the belt and they wear out pretty quickly.

Running the tensioner on the back side of the belt will allow you to force the belt to wrap around the pulley more...with a longer belt of course, but it is not the best way to do things with V-Belts.

This is but one of the reasons the makers went away from single V-Belts.
The Poly-V Belts are capable of transfering more torque in a smaller area and being wrapped around the pulley more with less issues.

V-Belts run on a few principles.
Look at the side view of a V-belt.
The cord body you see is where the power is transfered.
The rubber V below the cord body is there to keep the belt from being forced inot the pulley groove.
The rubber above the cord body is there to give substance and stability to the cord body.

V-Belts squeal because they are slipping...I know. EVERYBODY knows that.
But did you know the slip can come from worn pulleys, worn belts, dry belts, overheated belts, wrong sized belt for the pulley groove depth and groove angle, improper tension, belt whip, contamination in the air or directly on the belt.

The belt size, and pulley diameter/contact area play a big role in the amount of power a belt can transfer.

With your one wire alternator keep in mind it was probably designed for use with a poly-V Belt rather than a single V-Belt.
The poly-V Belt is capable of transfering much more torque than a single V-Belt and often poly-V pulley is designed smaller in diameter too. This often results in a smallish single V pulley being installed on the alternator in order to keep the same speed as the original intended use...and this often does not correlate to a good fit with the FE installation.

Worn pulleys get a bulge cut into them where the cord body of the V-Belt rides. Once this worn area is deep enough (does not look like much wear) the new V-Belt can not transfer proper torque because the cord body is not in proper contact with the pulley.
The belt will slip, squeal, and wear quickly but then a new issue pops up.
The belt is no longer a linear sided V-belt. Instead it now has a weird bulge shape to match the pulley and this never allows for full power transfer...It also causes other issues.

If the pulley has the correct depth and angle, and is not worn.
If the belt is the correct size (V shape, angle and depth) and riding at the correct depth in the pulley. (the V-Belt should be almost flush with the top of the pulley, or slightly recessed in the pulley, not sticking up any amount above the pulley.)
If the contact area around the pulley is maximized for the application and location and you still get belt slip...Then you need to change to more pulleys in order to transfer the required power.