Will the A650E 5spd auto on 98-2000 sc fit the older models? If so what would be the benefits if any.

 

Yes they will physically, and the extra gear would be the benefit and you would also install the gated shifter.
The problem would be controlling it not sure what ecu's will need to be changed and also some wiring.

 

Thanks, I've searched the wed but most swaps are the obvious manual swap.

 

It will probably be easiest to do if you were dropping in the whole motorset, the vvti engine and the 5 spd auto trans as it would probably simplify alot of the wiring making it more of a drop in project. You will probably have to use the vvti ecu (300 or 400) to be able to control the 5 spd auto, and you may get cel's if you have it on a non vvti motor if installing into an older motor in the case of only swapping the trans, and then you have to start making choices. the whole motorset engine trans and ecu would be the easiest way to go I imagine.