8 3/4" Mopar gears have a reputation of being a weak link and need to be watched/checked. But I've gotten more life out of them with REM finishing and cryo treatment at Evans Performance near Atlanta, GA. They do both and I believe they have a dry film coating that can be used on ring & pinions as well. You'll have to do some shipping no matter where you buy from, but apparently they can buy parts as well. You can do some cost crunching to see what would work best.
http://www.evansperformance.com/home2.html
With the REM finish, my differential guy sets them up before treatment because the highly polished surface makes it difficult to get a clear pattern.