Whitedog there is another tough option for a 3/4 ton. Look into the GM version of the A833 overdrive 4 speed. They pop up freequently, and are tough as nails. An NV4500 would also be an excellent choice as it is a 5 speed with a granny low, and a .73 overdrive. I put one in my 59 GMC 1/2 ton behind the original 336 V8, and will also be putting one in my 1940 3/4 ton behind a well built 302 6 cylinder. The NV4500s are a bit pricey. They do a great job moving an old truck that still wants to work.
