is there such a thing as a 8 1/4?

I've got a 68 Barracuda which has been through a bunch of owners. I've tracked down 3 of them and haven't gotten many answers from them so here I go. I crawled under my rear end And coppied down these numbers.
3723599
46671
KD 43

Can anyone help me identify this rear end. The car has a 318 and a 4-speed.