I put a Chev Nova rear end in my 46, haven't driven it yet but it looks alright. took it all apart to check the gears etc, everything looked good so sealed it back up, sanded and painted it and it looks like new. Had to rebuild the rear brakes and cylinders but thats normal. My 46 also has a Chev S10 front end. Trying to fit the 350 drivetrain was tricky but I got it in. Looks a little narrow in the front end but wide tires will cure that. Good luck in finding a good differential. Bob T