I also have a 1991 Explorer that I have been considering a V8 conversion using a fullsize (ZF) transmission. I have a running 1987 302 from my buddy's 1987 bronco. I am considering using an Advance Adapters fullsize Ford to stock 1354 Explorer case adapter. it measures four inches long ad costs about 400 dollars. This is not a for sure part of the plan yet, but the idea to use the full size 5 speed is. I would be very interested to see if you pursue this and would like to compare notes of what works or not. Rick