CRT.5 servo saver alternative?

So far all ive actualy atempted to use was the center front and rear drive cups that are the same and work well.I also expect that the diffs are the same but the OFNA guys cant or wont confirm ya or nay.but ive considered trying to use the 40 tooth spur to have more gearing options and if the cap joints are the same and the wheel drive cups are well ,you see were im going but i dont know for sure yet .