360, check out stuff like pistons for 318 motors and then 360 pistons. The 360 has more brands and styles and if they offer a 318 piston in the same style its like always more money.
If your going to rebuild one try to find a 1971 to 74 motor.
Either one is fine with me! I like the 318 for it's hi winding peaky torque. The 360 has lots of grunt down low and through the mid range yet can wind right up as well.
Oh yea! I second that and alot of it in stroke for lots-o-torque. just the thing to get the car moving. Pistons are cheaper and the heads have lots more potentail.