would a nv4500 out of a 96 chevy bolt up to a 89 12 valve? or do you have to use an adapter

 

different bell housing and input shaft but then yes it would bolt up, u may have to change the engine backing plate i'm not 100% on that one

 

So many variables here.
Do you plan to swap to a Dodge Diesel input and bearing retainer?
Chevy uses a 1-1/8" by 10 spline input, Dodge uses a 1-1/4" X 10 spline input.

You also need the '94-'02 Dodge block plate, starter, flywheel and clutch.

You CAN put the Chevy bell and block plate on, then run a Chevy style flywheel, clutch and starter, but if you don't happen HAVE the Cummins-to-Chevy stuff, the Dodge stuff is much, much cheaper to get.
I've seen the Chevy flywheels SELL for $800.

Also, the more commonly available Chevy block plates that are out there, tilt the engine 15 degrees to the passenger's side.

Mark.