340 vs 360
Realest:
Unless you are going for originality, do a 360. I've built 3-4 360s from almost junkyard parts: Use mid-late truck motors or cop mills as a starters and do some research to see what years had shot peened cranks and rods. A little bit of head work, careful cam selection, 4 bbl intake and a tuned thermoquad will give camaros and mustangs fits. You could build a 325hp (maybe more ?) engine for under $1k if you start with the right parts.
Good luck
Trevor