As a warning, some of the internal pieces on early (pre-'71) CIH transmissions are quite different from the later (1971 to 1975) models. I ran into this when I re-built Kat's '71 GT tranny, and had hoped to use the internals from a spare '70 tranny she had. On her '71 tranny, the pilot bearing had piled up, which in turn piled up the front main tranny bearing, which in turn piled up the inner needle bearing, where the input shaft and main shaft run together inside the tranny case. Well, one caused the other which caused the other. Anyway, I was able to use the old style input shaft (the one that sticks out the front of the transmission and is driven by the clutch disk) in the newer style housing, but the main shaft is unique. Mainly it's the speedo gear that is different, as well as the 1st-2nd gear synchro.Wayne said:
And it's not so simple as to just swap the transmissions. Although they are essentially the same (aside from the key internal pieces I just mentioned), the speedo drives are on different sides, and the early model uses a right angle gear reduction drive. So the later speedo cable won't reach the early speedo drive. It might work the other way, but something tells me the speedometer ratios are also different.
HTH