8 3/4 Rearend bolt size for Pinion Snubber

I have tried 7/16" bolts and 3/8"x16 and 3/8"x24 and nothing seems to be the right size for mounting my pinion snubber on my 8 3/4" rearend. Does anyone know what size bolts fits? The rearend is all ready mounted, so it is hard to see if it is even threaded.

Thanks

bwhitejr