Would a transmission from a 1993-94 ford ranger lariet be compatible with a 1990 model?

Can they be interchanged? Or looking for used/rebuilt transmission for 1990 model… Automatic with 2.9 liter,6 cyclinder

Nope.

You need an 89-90 AOD.

Not many used out there, but a few are here; http://car-part.com/

I have had to rebuild mine twice over 450,000 miles.

No, the 93-94 is going to be electronically controlled. You need a non-electronic AOD with the throttle valve cable.