if money is an issue ya a 393 would be the way to go. as far as horsepower 15 cubes ant gonna mean a hole lot but every little bit helps i think 373 would be to much 355 would be better but thats just me. most will say go 373. as far as tranny gos built c4, c6, tko 500 or 600 ( i would go 600 for taller first gear) or a t-56 six speed (holly grail). hope this helps