86 Black Roller 318, swap/interchange into 72 318
the 86 short block seems like the winner here. i'd build from there if it were me. heads are easy and all that.
realistically, you don't get anything from the 73 crank. it's a little more laurent le boeuf but it's (probably) cast, same same stroke, probably heavier, and you have to deal with the whole balancing thing. so bragging rights, maybe.
dress it old school and nobody is gonna know the difference between a 86 and 72 unless you told them