You need side gears that will accept a half-shaft circlip. Side gears designed for axle C-clips will not allow the half-shaft to lock in place, because the groove isn't located correctly. I don't remember off the top of my head which brands of differentials are circlip compatible, the best thing to do would be call the manufacturer tech line. I can tell you that currently the Eaton Carbon-fiber Positraction is NOT circlip compatible, and requires disassembly and machine work on the side gears to use on the SC. (Believe me, I know all too well about this...) Supposedly Eaton is working on a circlip compatible version.