A833 4speed OD trans Swap Question

Yeah, it doesn't take much to machine.

I'm just thinking that a lot of steps can be skipped completely and money saved, if the original running gear has the same number of spline teeth on the output shaft as the new O/D trans has.

If that's the case, the O/D gears and shafts will all go straight into the original transmission casing that the car has, with absolutely no modifications needed. The 307 and 308 bearings all have the same I.D., so the overdrive shafts and gears will work, as long as the output shaft splines are the same between the two transmissions, the driveshaft will fit correctly into the housing, with the O/D gears swapped over to the original case.

For that matter, if it's a numbers matching car, the transmission would still appear to be original.