i bought an eaton kit with the gears and everything on ebay for cheap as hell the other day. the kit just arrived and when i opened it the eaton and the install kit were for gm, the ring set says motive f8.8-373 on the box. i took these to a friends house to compare to some old gears he had lying around and they look identical. are the ford 8.8 3.73s and gm 8.5s the same or are these boxed wrong. im waiting till the place i bought them from is open so i can call but this is weird.

 

Not the same. Check the pinion spline and pinion diameter at the bearing areas, that will tell you if they are the same gears. The box may just be mis labeled if they are the same.