my427stang,i had an original 68 1/2 cobra jet fastback that had the no 2 main with a large crack in the threads.lost oil pressure.everything else was nice,but a mostly stock engine.junked the block,later sold the car.

We work on all FE heads…….every kind of OE head, and every kind of aftermarket head.  Lots of people blow about the Trick Flow heads.  They are good heads.  I send a lot of BBM heads to people and shops that know about the newer BBM heads.  I find it odd that no one who is telling you the TFS heads are better “bang for the buck” have bought any of these BBMs.  I know this because I know where I send them.  They are a little bit more money, but the prices have remained the same, and will remain the same until I run out of castings and have to address that.  So if they cost a little more, and perform better, what is the yardstick for “bang for the buck” when the lesser expensive head does not perform as well?  It is a bit of an uninformed opinion if there is no comparative data.  One might argue that a standard Edelbrock is the best bang for the buck.  It is much less money, and also makes less power, but what is the yardstick?  How much more, incrementally, is a person willing to pay, for increased performance, incrementally?  It just depends on the individual.

 I have had or do have just about every kind of FE head there is here, or they have been at one time or another.  Just for what it’s worth, I had iron Cobra Jet heads with 2.09 valves 20 years ago that would outperform the current Trick Flow heads.  Obviously they were/are extensively worked, and expensive, but Mr. Lykins just posted that the TFS would be “way better” than any LR or MR head, even if ported. That is an incorrect statement.  Like I said, the Trick Flow heads are good.  I use quite a bit of their parts, FE and otherwise, but they are not the only show in town. The C4-G Engine Masters iron heads are not far off the Trick Flow on 400-ish cubes, and these days cost less. The usual comments about my engines are that the dyno must be wrong.  We didn’t use my dyno at Engine Masters, and those old iron heads made 600 hp there, with 10.5 CR and .575 lift, on 396 inches.  Not sure what the definition of “way better” is.  Those were not Super Stock heads.  No epoxy in the intake port, no brass in the exhaust. Less than 3K for a pair.  They are not always shelf ready either, so I generally default to the BBMs, of which we have plenty , at this time.   I am not, by any means bashing Trick Flow.  I am simply making the point that they are not alone.  I spend a lot more time working on heads than I do pecking on a keyboard.  I don’t really have time to properly market my junk, so it is often left out of these posts.  I generally don’t say too much anymore.  I don’t post everything we run in the dyno section.  I am going to post one next week.  BBM “F” version heads, 13.5 CR, Trick Flow tunnel wedge, 520 cubes.  We’ll see how that shakes out.  Thank you Frank for the honorable mention!

Lets not forget Blair's BBM heads.

Very bit as good, if not mostly better than the TFS heads. Maybe a couple of bucks more but, you'll need to talk to him. Could even be cheaper now TFS keeps going up:

BBM FE CYLINDER HEADS

BBM has been manufacturing and selling high quality Ford FE cylinder heads for over a decade now.  For over ten years, we have been working with Blair Patrick Enterprises for final prep of our complete head packages.  We are excited to announce our latest updated castings!   BBM and Blair Patrick Enterprises have developed new intake and exhaust ports, and updated our chamber to produce a new high quality casting, with improved flow, efficiency, and performance.  There are more port options and expanded valve spring options available. Intake valve sizes 2.100, 2.200, 2.220, and 2.250. Exhaust valve sizes 1.625, 1.665, and 1.680.  Sales of the new heads are being handled by Blair Patrick Enterprises.  Blair will work with you to be sure we provide you with the best port, valve sizing, and hardware options to suit your specific needs.  Contact Blair Patrick and let us tailor your heads for your application based on years of successful experience in the FE community.   BPE can also provide you with top end packages, camshaft and valvetrain components, rotating assemblies, or complete engines using BBM cylinder heads. Email blairpatrickfe@gmail.com to take advantage of our updated castings, coupled with  BPE’s 40+ years of FE experience to get the most out of your combination.

With the bigger heads, you can get results such as this 1.66 hp per ci, 839 hp, 504 ci killer:

https://fepower.net/simplemachinesforum/index.php?topic=13305.0

Well yeah, that's why I knew even way back then to choose a cam with more exhaust duration. And I know we still choose cam lobes based on some of this. And I know there are other benefits besides flow to a modern cylinder head design. Combustion chamber being high on the list.
But how much potential loss... 15-20? 30-50?
I know... it depends. Just spit balling thoughts.

Intake/exhaust flow ratio data is still very important.  Camshafts are ground around that.

With that being said, even with an "undesirable" header, the TFS is going to be way ahead of any factory LR or MR cylinder head, even with work done to them.