[TheJackRabbit]

I have a 1979 GMC 3500 short wheel base dually flatbed with 4:88 diff gears, the Muncie 4 speed and a recently built 383 (carb). It likes to cruise about 55 MPH. Now that I am using this truck more, it sure would be nice to have that 5th gear overdrive. How big a project is it to refit it with a tranny like the NV 4500(?) that some folks use when they convert their Land Cruiser to a V8? Is there another tranny that matches the bell housing bolt pattern of these older trucks or am I looking at some major adaption?

I am guessing that a tranny upgrade is less costly than adding one of the Gear Vendors gear splitter ODs. Am I right about that or is that a better way to go?

Any advice is appreciated.