This has been discussed at length on the Ford Truck Enthusiasts forum in
this thread. There are many options for overdrive that I cover in
this post. My recommendation is to swap a 3.00 ratio 9 inch rear axle in and use a heavy three transmission since all of this can be done with no cutting of the frame.
rotorwrench, the T86 is a top loader and a lot of them have overdrive. A Jeep 3 speed shifter bolts right on. Check this out:
http://www.google.com/imgres?imgurl=...t:429,r:27,s:0