On the 4 speed, I assume you have the one with the reverse lever on the stick. That's not the tranny I would choose. Both trannies are synchro except for first gear, and since second gear in the 4 speed is about the same as first in the 3 speed, that is an advantage. Reverse in the 4 speed is considerably lower than the 3 speed, which I like, but that's a personal preference. Granny gear is rarely used, but nice to have. If it were me, I would get the SM420, 4 speed from the 48 to 66 model, which doesn't have the lever, and is a good tranny.
