my uncles 66 gmc 3/4 ton had the 4 speed tranny in it and not sure what the rearend was probably 3:73 when i had it i don't remember winding it up like a 9 day clock. you could run 55 or 60 easy. still doing research but am leaning towards 4 speed in front of a 3:73. then i will have to figure out how to attach the axel to the truck. :/
