2.43 1st Super T10 is going to like a 3.73:1 or higher rear axle ratio. TH400 is a bit overkill; a built TH350 from a specialty shop (not necessarily the 'catalog stores' can do the job)
The T10 (aside from the 3.42 1st gear) or a good condition M20 Muncie is adequate assuming street tires a soft clutch and not powershifting.
If I was on a budget; I would use a prepped 700r4 and 4.11s or a prepped th350 and 3.55s or 3.73s.
If I wanted a manual; I would get a good late T10 or good M20 and run 3.55s
If you go the muncie route, I would use the iron midplate and perhaps a brand new maincase to add strength