Ran the car today on a DynoJet just to get a baseline.  Basically, I'm not really happy with the way the car pulls but I've been playing with the tune and can't really seem to get it much better.  Last night I pulled 2* of timing out of it to be safe and hit the dyno this morning. 

390ci
Holley 750dp
Performer RPM
Edelbrock heads with light bowl cleanup
Comp 270H 224*/.519" on a 110LSA, installed at 106
9.5:1
FPA 1 3/4" TriYs



So, it peaked at 302hp at 5400, 369ftlbs at 3500.  As a reference, made 280hp with 3* less timing in it, and sounded and drove a ton lazier so big difference.

Numbers back up how it feels in the car, it's a torquer around town, kind of surprised it made peak power at 5400 as it feels flat after 5000rpm. 

Flywheel numbers, which I'll estimate since I think guys are more familiar, would be 380hp/460ft lbs using 20% loss. I figure my setup, optimally, would make 400hp on an engine dyno, throw exhaust on it I guess this isn't too bad.  Not sure I'd believe 460ftlbs as I don't think any similar builds come close to that number. 

If you read the AFR chart though (the dotted red line is 12.5:1), car is tuned fairly well on the hit, but then goes dead fat until 4200rpm or so.  That's about how it feels if you roll into it in say 3rd gear and it has some gear to work against....very soggy.  The peak A/F ratio at peak is perfect so not sure I'd mess with the jets, just not sure how to lean it out before that point?  I don't think a lower power valve would make much difference as this is WOT and I'd think vacuum drops immediately.  Any ideas?

Just piling on with what's been said.  The lift block acts as a lever and really moves the pinion around on trucks, as I'm sure you've guessed.  I had my 390 in a '76 F250, very heavy duty springs, and i had pinion issues.  I put new springs in it with no block and the pinion walked much less.  It's amazing how much they'll rotate even at light cruise.  I know your truck isn't that heavy, but it's heavy enough and with somewhat large tires, it's using a fair bit of torque even at "cruise" compared to a car. 

258cfm would be hellacious exhaust flow for a "street oriented" FE head.  Just going by some modern FE castings, they're doing well to achieve 72% exhaust to intake flow ratio (using some posted figures for BBMs and Felony)

If it flowed 258cfm, the intake would be flowing in the 360cfm using the 72% ratio as "rule of thumb".  Don't see that happening with a 175cc intake port.  Of course, they could be skewed with a really good, slightly raised exhaust port, and hit an 80% ratio, so call it 325cfm on the intake side if that were the case, I see that as "maybe" possible with a good CNC intake port but have my doubts it can happen at .500" with a small port.  The Colvert/Kuntz CNC BBM heads go 321/226 at .500", but they're more in the area of 195cc intake volume. 

It's all conjecture at this point, obviously, just thinking out loud. 

I've had a little time to put miles on my TKO 500 combo now as well, Ross.  Background info, 390/TKO 500 with .68OD/4.10gear/'63 Marauder.  I have same rear tires as Ross, 275/60/15s, so RPM/MPH info is the same. 

I run a 750dp/Performer RPM/Comp 270H which is 224* on a 110LSA advanced 4*.   So, 100cubes less, fatter car with more frontal profile, cam is smaller but I'd bet a 224* in a 390 is same ballpark RPM and vacuum wise as a 242* cam in a 489?  I always went by the rule of thumb of adding 6-8* of duration for every 50ci of displacement to keep RPM range the same.  I'd also guess your solid may act a bit "smaller" even with the tight lash, but splitting hairs. 

I just drove it down to Va International Raceway last week, 400mi round trip.  Ran mostly 60-65mph, car pulls great at the 2000rpm cruise.  We were on a secondary two lane with some quick "rollers" through the foothills that were fairly steep and they just required a little roll into the throttle, no problem.   Slower sections through town 45mph/1500rpm, just for fun I stayed in OD, it will handle it but throttle response is basically nil and it does one "chug and go" when rolling back on it, but it doesn't buck.  I'm sure if I wanted to play with the power valve I could get it to pull clean at 45mph but I'm not going to be in the habit of lugging it.   55mph is 1750ish rpm, no issues and pulls clean, will gain RPM on uphills with a little throttle so doesn't feel like it needs a downshift. 

I'd say this gear/trans combo is "perfect" for my needs.  Virginia has a bunch of really nice two lanes so the 60-65mph zone works well.  I have spun it up to 70-75mph for long stretches (75 is 2500rpm) and that works well too, so I can hang with interstate traffic just fine as well if needed.  The SLR is pretty steep with the 3.27 first, but it works well to get the heavy car moving.  Also, I had to extend the z bar arm to work in my car, losing a ton of leverage on the clutch, making it very "heavy".  With the deep first gear I can actually roll along at idle in traffic situations without bucking, nice to not have to keep working that heavy clutch pedal.

Granted, my combo is very mild.  As has been stated already, trying to figure out the sweet spot for more street/strip type stuff would be interesting, especially for smaller displacement stuff.   

360hp/420ftlbs

Very similar combo with more cam made 390hp, along with a few other examples.  Stock head combos with street cams are going to struggle to hit 400hp on 390ci unless they've been rubbed on quite a bit.

https://www.youtube.com/watch?v=PjxO7sND__Q

https://www.youtube.com/watch?v=vEJUXUJfFQs

Don't see too much about these motors, being just a two year option.  Was always curious how they'd run with the solid cam as it seems to match the big ports better, pretty impressive 6000rpm peak.

Everyone knows the 375hp rating was bogus, but the Holley and solid cam seemed to really wake these up.  My understanding is stock cam is 226/238 .509/.509 on a 114.  Don't have the time to lookup how that compares to 427 cams?

Thanks.  I drove the car for a short time with 3.00s in it and it got 15-16, since then I ran it with 3.50s and then 4.10s, I don't really check it as it's too depressing but last time it was around 9mpg.  The overdrive turns the 4.10 into effective 2.78 gear, so it should do 16mpg again.   

Finally updating after a lot of trial and error.  So, I had a very early bellhousing in the car which had a clutch fork opening around 10 o'clock.  I checked a bunch of bells at Carlisle and these seem to be pre 62 from what I can tell, didn't dig too much as I already sold the old bell.  The "normal" FE bells have a clutch fork opening down around 8 o'clock, so my bottom arm of the z bar was too short now to line up with the lower position of the clutch fork.  I tried to monkey around with it anyway and see if it would work even with the offset, as it's a major pain in the ass to pull the z bar in my car with the headers installed.  Long story short, wouldn't work as I could only get .015-020" of air gap at the clutch even extended the upper clutch linkage a bit to give it more throw. 

So, I pulled the z bar and extended the lower arm 3" to match the new position of the clutch fork.  Clearance is pretty tight between the block and headers where the extended arm hangs down, but it all clears.