Both Spicer and Clark made 5-speed overgear transmissions that have the Early GM bolt pattern. I understand that Clarks are hard to find parts for but the Spicers may still be an option. There are old-time truck wrecking yards still where you might pick one up. Aside from a little hammer work on the floor pan it's a bolt-in. Being truck transmissions of another era, they still aren't quiet but hell-for-stout compared to a T5. At the ATHS show in Salina UT a fellow looking at my 4x3 setup said, "ya know they make a 10-speed road ranger for light duty... Top gear on a Road Ranger is an overdrive, around 0.85 or so. I still have the 4x3 setup.
