You should make absolutely sure the flywheel and balancer are match for the motors type of balancing
I bought a 1976 400 short block out of a 1976 dodge 3/4 ton pickup, it had a forged steel crank and a thin balancer
I didn't get to see the flywheel so I'm not sure if that motor was internally balanced or not The balancer had a bunch of holes drill in the back side of the outer ring, all on one side