The list of cars the Saginaws were installed in will basically cover any low horsepower GM passenger car that came with a low power motor and 4-speed from the late 60s up through the early 80s. The grooves are cut across the input splines and should be very apparent if there. Since you do not see them, you trans is most likely a 2.85 first gear.
I do not believe the transmissions were painted from the factory; someone may have painted it when it was installed in another vehicle or rebuilt. If your search for the tranny's origin is to find normal rebuild parts, most tranny suppliers just need to know it is a Saginaw 4-speed and its first gear ratio. Six-states may still have the parts in inventory. If you need internal gears some are very hard to find and may cost more than it is worth.
