I am in the process of putting an overdrive in one of my 3/4 ton pickups. It is a chevy front box with a Warner .70 overdrive. It is the same overdrive that Ford used in their T86 which was offered with about 300 cu in engine. That's a whole lot easier to do and .70 OD with 4.56 rear is better than .80. I had a Brownie in an old truck tractor and was going to put it in my 57 GMC wrecker, but it fell victim to moonlight auto parts. They left the shifter which resembles the stick on a SM 420. Usually they were mounted between the driver and the door. As OldSub said,its a lot of trouble for 20% reduction in rpm. Of course I guess you could lock it into OD and not worry about shift linkage. I think the smallest one I have seen is about 400lbs.