You couldn't adapt a V6 a4ld box to fit the 4 pot afaik - could just fit the car with a 24v lump and box though -the easy and cheap way to 220 brake.
Whether the 4 pot a4ld (2.3 scorpio etc.) box can handle the power I am not sure, ok, it probably could have when new and attached to a standard YB.

I'd go along the route of fitting an engine designed for an auto box (FBA, yank V8, Honda/Lexus/Supra or summat) or fitting manual hand controls.
Jojo from the XROC has a XR4x4 2.9 with hand controls for the manual box if you want any info..