86 Black Roller 318, swap/interchange into 72 318

AJ/FormS said
What's wrong with using the 318 crank that is already in the engine? Even if it's cast, How many broken 318 street-cranks have you ever seen? or heard of?

I bought a 72 Barracuda from an old girl friend many moons ago. I got it real cheap, 318-broken crank. that is the only one I have ever seen.