360 or 383?

Big block auto trans missions are not hard to find - SharaDon Performance in Hugo MN has 35 of them...

I vote the 383 simply cause I am in the middle of putting one in my Demon

You have the fenderwell or hedman b body header option to keep cost down, swap mounts are $62 for slant to B/Rb/ $69 for slant to small block/ small block to big block are $65

440source makes nice aluminum heads as well as aluminum water pump housings for cheap - mill those heads and run them - plenty big for a stock 383 to make good power

Only need 1 intake for a big block race car = M1 w/ a 750 holley

you'll need a hood scoop, or just rock no hood = 100lbs off the front

IF that $400 motor runs, leave the rotating assembly, and build a decent top end, and a decent cam, run the shim head gaskets to get the compression up