There are no casting numbers or markings on the transmission that specifically designate the SM319 OD. It will have an R10 H or K designator on the OD unit however. They were used from 1955 through 1965 in both cars and trucks. The differences are the side cover and lower mount holes threaded on trucks. This trans uses basically the same case and internal gears as your current SM318 with a BW R-10 overdrive replacing the tail shaft portion. There are 6 volt solenoids available as other manufacturers used od's in 6 volt vehicles prior to 55. You would also need a 6 volt relay for it to operate if this is your plan. It would probably be better to convert to 12 volts.
There is lots of information on this site regarding overdrives including pictures and wiring diagrams.
Fred
Last edited by rfs56trk; 06/04/2015 4:33 PM.
