Barnfind49 - From 1964-66 (and perhaps later?), Chevrolet offered an optional Borg Warner T-89 "heavy duty" 3 speed with overdrive in the pickup truck line.
I came across this ad that looks like it's offering a
T89B that would also fit your application if you can't find a Saginaw 3 speed OD equipped transmission. The picture shows a 1968 casting date on the unit.
At just $100 asking price, it sounds like a great deal. The ad does say "door pickup" and indicates it's in Nashville, Michigan, so maybe a long roadtrip needed to capture this one.
I'll keep looking for a Saginaw in case this won't work for you either.
