Thanks for the pictures of your truck. It looks like a great old truck!

Many years back, a knowledgeable Dodge truck guy told me there were a FEW overdrive 5 speeds used in the medium duty trucks. Unfortunately, most of the 5 speeds were direct drive in 5th gear though. Attempting to locate one of these rare overdrive transmissions might be nearly impossible. Of course, locating accurate information on such an unusual truck probably is not real easy either!

I wonder if a transmission out of another brand of truck would bolt up to the bellhousing in your truck?