Just so you know, the Chevy Muncie 5-speed you would like to use does not have a removable bell housing like earlier transmissions. Therefore, you would need an adapter for Chevy automatics to nailhead, and still would have to come up with a pilot bushing or bearing that fits either the adapter crank spacer or the crankshaft itself.
If you wanted an automatic (which it seems that you do not) I have a ST 400 core listed in the classifieds. This is just like a turbo 400 but bolts directly to a nailhead, although it still requires a crank adapter for pre-64 nailheads, which all 364's are.
Good luck!
440shorty
P.S. The Tremec TKO 5-speeds, which physically interchange with the T5, are strong enough for that nailhead torque, but could be adapted to a nailhead straight drive bellhousing, if you already have one.
P.P.S. The GM Muncie 5-speed is not as great as they may seem. Check out this link:
http://67-72chevytrucks.com/vboard/archive/index.php/t-215637.html