Gobso,
All the three-speed trannies had unsynchronized first gear up until 1967 (?); first in my '64 C-10 was still un-synced, anyway.
If the bushings in the shifter linkage are worn, you can have a real hard time shifting- the usual symptom is for the trans to be in second while the column lever looks like it's in "neutral", and won't move from there. This usually happens at an intersection during heavy traffic with the truck headed up-hill and the only cure is to shut down the engine, set the parking brake (or brick ,whichever is in working order) and getting under the hood and grabbing the shift rods and working them around until things unbind and the tranny finally goes into neutral (usually accompanied by a symphony of horns from surrounding cars!).
At any rate, "any" 1948 to 1963 three-speed will bolt to the bell housing; the output end is another story. All pre-'54 3-speeds up through 3/4 ton had an enclosed (torque tube) type universal joint at the rear of the tranny.
1/2 tons had the torque tube all the way back to the differential. The 3/4 tons had a short "torque tube" back to the center carrier bearing, then open back to the differential.
1955 and later transmissions had the long extension housing w/ the fine splines and slip-joint on the rear tranny shaft.
One other thing, my '54 began to be really difficult to shift into first gear: turned out to be a collapsed front cab mount, which allowed the cab to "slide down" the steering column enough for the first/reverse shifter lever to hit against the bottom of the toe-board, so make sure your cab geometry is ok too.
Good luck!
Frank 54
