Awesome info.
Thank you for taking the time to respond as you did.
I really appreciate the advice and the reasoning why.

So .... no Muncie for me. I want to keep my 3.08 gears and don't want to change out carrier, gears, etc. for lower "Muncie appropriate" gears. When it comes down to it, this car is babied by me. Never doing burnouts, just love driving her, both in town and on short highway runs where she does 65 easily at this point with the TH350. But I would enjoy a snappier start, and certainly want a 4 speed.

I'm fine with a Saginaw, despite the bad antidotal stories of them blowing up with abuse. I don't plan to beat it beyond the rare "chirp" from the tires. On a retired budget, I simply don't have enough cash to break stuff intentionally and I prefer the rubber on my expensive tires, not the pavement behind me !

Saginaw (411) 4 speed with 3.50 first gear gets me 10.78:1 ratio with my 3.08 gears (I found a nice one rebuilt)
Saginaw 4 speed with 3.11 first gear gets me 9.58:1 ratio with my 3.08 gears (all that I can find are questionable)
I know the Pontiac 400 has more torque than the Saginaw was designed, but I'm not going to be seeing such high torque in lower RPMs with my driving style.

Thoughts ???

Thank you again.