Well, this isn't all confirmed yet but my builder has my transmission & was getting a LSD diff installed because my stock one broke. Basically without getting into a long story, I thought I had a GSR tranny & he's saying its a LS but someone put an GSR Diff in it which we all know shouldn't be there. I simply, for right now need to know if a GSR Diff can fit into a LS or rather can a LS ring gear fit onto a GSR diff. He is saying that he counted the teeth "64/15=4.2666 ratio", which is an LS FD but correct me if i'm wrong but I thought a LS FD cannot fit onto a GSR Diff. Isn't the LS diff physically smaller & the ring gear wouldn't swap over to a gsr?