On the 1963 rear end there is a number CJ 18 63. I know the CJ stands for 3.08:1 ratio but what are the other numbers, maybe Jan 8th, 1963. Also the little black book for 63 states as an option "G91 Special Highway 3.08:1 Axle (not posi). According to another book the CJ is for positraction but when I was checking the rear brakes with one rear tire on the ground and the other on a jack, I could rotate the tire on the jack. So if it was a posi, should I be able to do that.