The ring and pinion I believe should be something like 43/9 with the pinion having somewhere around 30 or so splines on the end opposite where it contacts the ring. I have done some more research as well, and the GM and Corporate names mean the same thing. I have also read several places that the 10bolt/12 bolt reference means the number of bolts holding the ring gear in place., not the differential cover or third member. I wonder if they use the same internal gears even though the GM diffs aren't third member designs. I would also like you to check if you get the chance the diameter of the front ring. It seems there are several different diameters for this listed under GM 10 bolts. If this stuff does end up matching up, then we have seriously stumbled upon something awesome.