Bill: Thanks for the input.
(more background). I'm in the process of sorting out and determining root causes of reoccuring issues with the car.

It's clear that the previous owner didnt want to get his hands dirty and maintain it; there was a sloppy original engine/trans install; and lousy service from the tech that he went to.

The guy spent a lot of money and the problems he brought it in for didnt get fixed right. So, we're working through exhaust manifold leaks, engine cutting out, backfires, electrical issues, malfunctioning tank fuel level gage, plug wires problems to resolve and fix. etc.
The poor guy spent a lot of money and didnt get a lot for it. For example, I found that the (reoccuring) exhaust manifold leak was caused by misalignment of the header flange with the cylinder head and paper thin gaskets. The tech who did the original fix should have picked up on this and adjusted the header alignment and used thicker gaskets.

To make a long story short, I'm just about 90% through with the trouble shooting now. I had it on the dyno last week as a diagnostic step, did several pulls, got the timing set properly, and got the carb adjusted so the car would run halfway decent with no carb mods (jetting etc). At that point I stopped. I got a first readout on where the A/F ratio stands and Hp.
With just the simple changes and a little carb adjustments, the rear wheel Hp went from 307 to 350Hp, torque 348 to 364 ft-lb. The A/F flat lined at about 10, so we're still pretty rich. THe engine's a crate Ford 393, 475Hp. I'd attach the dyno chart for interest, but cant figger out how to do it.

So, the next step is to do the final fine tuning (on the dyno) to get my A/F ratios up. Before I take the next step, I'm trying to find options (now looking at carb replacement or keep the existing with jetting changes) that will get the job done without spending a lot of trial and error time on the dyno.
Bob

The Mustang Shop in Auburn is the only one I know of. See the link below.

ReMorton. With a 10:1 A/F ratio at days end you really do have a long way to go. I'll bet you could downsize your jets by 5-6 steps to get to a good fuel mix. If renting dyno time is getting too expensive buy a new set of plugs, change jets and keep an eye on how the new plugs read and go from there.

The Mustang Shop / HorsePower Ranch Dyno Services

Try this URL and see if it helps
Trifecta Performance Custom Tuning :: Dealers, Independent Tuners and Affiliates

Another place in Auburn is Blood Enterprises. Craig Blood was able to dial in my dual 660's which was a chore. They are a mechanical secondary carb designed for drag racing.

blood enterprises -- automotive technology

ReMorton, So now I find out... I DON'T HAVE A HOLLEY DOUBLE PUMPER! When I was a kid, I knew everything about every new Mustang; price, options, etc. I even had the Ford Pricing book to memorize. Now I have the car of my dreams and I don't even know what kind of carb I have! Some parts on it are a Holley, but Bigs back East set up the carb and they must have had a special body because it doesn't say Holley on it. It works great, so I'm not unhappy with the equipment, just my understanding of what I got..... LOL!

+1 on That, Chas
Excellent Service, Excellent Help,

...Ward, since the work was done back east, check to see if the work might have been done by 'Guido', who as a sideline, does kneecaps and removes fingerprints with sulfuric acid. Make sure he wasnt practicing on your carb body..

Go with either QF or Proform. Proform is made by QF, just cheaper, but same as SS QF models. Don't mess with Holleys unless the tuner has modified carb for replaceable idle fuel restrictors and both idle and main air bleeds. With 10/1 A/F you definitely need more adjustability than just main fuel jets. I ditched my Holley 770 vac sec for a Proform 750 mech. Had to reduce idle fuel restrictors and increase main air bleeds, but well worth it. Engine (Roush 427SR) runs 14.5/1 cruise and 12.5/1 WOT. More power and 25mpg on highway!

SwiftDB4
I think that's where i'm headed. Your comments pretty much support what the guy at the dyno shop said, not enough 'knobs' for fine tuning to turn on the Holley (model 080508-3) compared to the other options I'm looking at, and my intended use for the car. The plugs are showing rich, mpg is about 15 and I expect a power boost with higher A/F ratio.
I could only find one negative reference to Proform, that was on the Camaro Forum. Apparently they offered a carb body, only, which you could use your Holley parts to complete the carb. It was pretty much a bust, and confirmed that yesterday when I talked to the shop.
So, the plan is install the Proform 67213, then put the car back on the dyno for the final tweaks then see what happens.
I'll have the before and after results. After the work is done, I'll post it here for anyone who's interested.
Thanks
Bob

Bob, are you using MPS on the guide?

Tim:
Yup
Bob