This one as stumped me. I have a gen two rear end with the following ID, casting is 1235542 with an N on top, date code is 6154 and here is the weird part, it is stamped CG G196 2 G and it looks like it has a 3:42 posi gears (haven’t open it up yet). It is in a 1973 trans am. Obviously this is not the original rear. As far as I can tell casting indicates 8.5 10 bolt, date code is June 15 1974 however the only place I can find CG axle ratios are 1971, 72 which indicates 3:73 posi. I’m sure the gears could have been changed I’m just puzzled over the ratio stamp not showing up anywhere in 1974.