The balancers will interchange. All 429s are internally ballanced. All early 460s are internally ballanced. In the late '70s Ford lightened up the crankshaft and blocks on the 460s. They externally balanced the engine with a counter-weighted crankshaft spacer. As long as you use the proper crank spacer with the proper crankshaft, you shouldn't have any problems.
--Mike
harmonic balancer ??
Linear Mode
