340 LA

72-74 engines are less desirable because of the lower compression, smaller valve heads and usually a cast crank. The pistons will be replaced and the heads redone (usually with some porting and larger valves) so a lot of that doesn't come into play.
A flip of the coin whether you just get a block and add your aluminum heads, intake, crank and the rest. Although having a complete engine with timing cover, hardware, brackets etc is a good idea. You may not use much of it depending on what you are building. Just food for thought.