Engine Swap Question

Just because it was mated when you got it does not mean it belonged. 68ish and earlier crank converter snout registers are smaller. That means if you have an earlier transmission mated to a later engine, the converter will not be properly piloted/ centered.

Mopar converters up until Magnums were weighted for external weighted/ balanced engines. All 273/318/340 that I'm aware of used neutral balance converters. A neutral balance converter may have small balancing weights, but not the larger one used on a 360. A photo would help

Same thing on the balancer. Who knows if it is original/ correct? Welding weights to "stuff" is ALWAYS suspect!!!!

I'm not an engine builder/ expert, but "it might be" that if you got some oddball crank/ rod/ piston combo it might be enough out of factory weight to no longer be balanced.