Don't they still sell the splines? Press out the old and insert the new?
It's not hard to find a good wing final for $35 or $50... a new ring gear is $250. You'd
either have to "butcher up" the new ring gear by robbing the splines from it, or
install it using skill similar (surly not as hard) to rebuilding an automatic
transmission (shims and stuff)... RickyD rebuilt his with all new...
-Mike