lots of variables here. depends what you wanna do. chevy 350 is very common, parts are everywhere. i don't like putting a carbed motor in if you wanna wheel it, so fuel injection gets pricey, throttle body being easiest.
my money is going into a jeep 4.0 stroker motor, it still uses all original parts, accept injectors which are easy to get. all factory computer and wiring from any 4.0 will work. trans are endless, i'm using a very low geared gm, but you could even use the ax15 that came factory also. and the stroker puts out better hp and torque numbers than a normal chevy 350, and the torque is at a much lower rpm where it is wanted in a jeep.