A contract instructor who worked for the Tennessee state trade school where I taught auto mechanics in the late 1980's had been an engineer with Saginaw when they developed those transmissions. They were designed for use behind the 4 cylinder Vega engines, the Pontiac Firebird OHC sixes, and other engines with low to moderate torque ratings. He claimed that in order to make them survive the torque of most V8 engines, they had to do some very special heat treating of the gears, and a lot of other upgrades. He said that he and a few other researchers went to the extra effort to beef up the individual transmissions they used in their own hotrod projects, but he was not imporessed with the Saginaw 4 speed for general use with high torque engines.
Jerry
Now that's a good question, what year was the R10Q-1 available? As not only was OD available in Saginaw 7-Bolt trucks, but a friend of mine had a '66 Chevelle Wagon with Factory OD.