I have obtained the following information based on research and working on these transmissions for many years.
Unfortunately the SM318 designation was used for the the torque tube transmissions as well as the open driveline units.
This is confusing because there were several variations over several years, some are noted above.
None of the gears and syncros from the open driveline transmissions can be used in the torque tube version.
55-57 cars used the long tail housing open driveline transmission. Also used in trucks from 55 through some 63's.
Corvette used the long tail housing but had a different gear set with a rear mount and a shifter mount.
58-65 cars used the short tail shaft version with a rear mount.
There was another gear set offered in 58 for cars with a 348 engine, it was also available in Pontiac's and later Corvette's.
It had a 2.47 first gear and a 1.53 second vs 2.94 and 1.68 in the standard version.
Trucks used the short tail shaft version from 63 through 67 with the standard gear set.
Overdrives (SM319) came with the standard gear set from 55-63.
64-65 overdrives and regular transmissions used gears, shafts and syncro units with a different pitch.
This version was also used in cars, Nova's, and Chevelle's. None of these components interchanged with the
earlier versions.
The Saganaw 3 speed full syncro w/overdrive (SM326) was available in 1966-69 in cars and trucks.
Fred
