What parts are you having trouble finding? Stuff like water pumps starters and alternators can be had anywhere as well as plugs and points.

Exhaust manifolds are famous for cracking especially the driver's side, and they are hard to find. If you find a set, take them to a machine shop and have the flanges milled because they are ALL warped and that is what cracks them. If yours aren't cracked do the same so they stay that way.

To answer your question, any LA motor will bolt in but as was posted a 360 will need a special B+M flexplate or a torque converter with a balance weight welded on it because it is externally balanced.

Kevin