I have everything you need for a 4-speed conversion, except the floor-hump and a reverse switch. Including 3 or more transmissions to chose from. Currently they are on the back-burner for assembly, with many new parts.
I could also rustle up an 8.75 with gears from 2.76 to 3.23, or even a slightly noisy 3.55 that I have been running for several decades. Also available are reconditioned cone-type SGs. all are small bolt pattern axles.