Snapper RER right hand differential all the same????

I need to replace a 1987 Snapper rer right hand differential assembly. Do all the older models use the same differential? What years are the same that I should look for?

If the top of the differential is rounded shaped and extends above the bottom of engine, that's the one. If it's squared off and level with bottom of engine get that one. I remember all the round tube frame models used the same rounded top one.