My question is pertaining to the torque converter on my dad's 85' Dodge 360.

He has recently rebuilt the engine and has converted it from an external balance to an internal balance crankshaft. Can he simply knock the counterweight off his external balance torque converter or does he need to replace the torque converter for an internal balance one?

He knocked the counterweight off and has been driving it on and off. Once in a while the truck starts to feel like its bouncing around as if it has a flat tire. Any ideas if the converter is the root of the problem?