The parts manual was printed in 1953. It is the light duty master parts book for models 100 through 370. There is an asterisk next to the 12V part numbers (and other options such as hydramatic). The legend for the asterisk states "Determine if option required." The starters and generator descriptions specifically state 12V. It is obvious that 12V was in fact available. Maybe not standard, but still available.
The M211 and M135 military trucks were 24V. Their predecessor, the CCKW was 6V. I had a pair of the M135 and my brother has two CCKWs.
