I can narrow your rear end to A body length and specs if that’s what you’re looking for. I’m in San Jose, and have narrowed dozens of 8 3/4 and 8.8 rear ends. If you can weld and have a jig you can do it yourself also.
You ideally want a 65-67 B body rear end, they are almost a bolt in. With the tapered axle rear you would probably want to weld new flanges on the housing ends and replace the axles and brakes with the newer style.
All explorers have either open 3.55 or 3.73, or limited slip 3.73 or 4.10. What I did was pull 3.27 gears out of a Mustang with 28 spline 8.8 and use them in the Explorer rear end. The ring and pinions will interchange with either axles.
65 transmissions are one year only, I believe they are cable operated. You will run into problems if you have an auto on the column and probably even the auto on the floor.