Thanks Bill,
I was flippin through my 1957 Motor's truck manual
and they show the standard '55-'57 3 speed as having the same input shaft that's on my OD.
The heavy duty 3 speed does have the larger input shaft however. If I did use the OD I would have to use a manual operated solenoid cable/lever like the one OverDrive Inc. sells because I don't plan on converting to 12 volt anytime soon.
