The 91 will have the TBI engine. I'd steer clear. 1992+ will have the magnum port injected engines. Big upgrade over the old tbi engine. Don't bother with the 3.9 V6 trucks, they get the same mpg as the 5.2 trucks and obviously a very notable power difference. The only way I would consider a V6 dakota is if it was a stick shift.

All the dakotas and rams of the 90's have crap auto transmissions. Best thing you can do is get one with a stick, next best thing is to buy a cheap one with a shot trans so when you're done you know you've got a fresh rebuild.