I apologize, I see now where it states about the pinion splines, that being the case that set is different than all the others.

No, I don’t believe the housing is different, the actual differential is a different size. I’m just thinking you can’t buy a set of 3:73 gears and bolt them up to a differential that came out with 3:15s or lower, I mean that’s obvious it says so in the description, why? It has to be that the differential is a different size and I’m just assuming here but I would think where the ring gear mounts it is smaller.