There was never a torque tube posi option. Chevrolet didn't offer Positraction on any vehicle until '57 (Passenger and Corvette). Chevrolet trucks got it in '59, and did not use the HO33 axle. They used the Spicer 45 from the GMC. That was a 1 year only axle for Chevrolet, '60-'62, possibly some '63s, have the Positraction HO33.
Just to clear up some confusion, there was a mention of the Positraction axle being a clutch pack type, and is more of a "limited slip" rather than a "positrac". Positraction is just GMs brand name for a limited slip differential, there is no difference. Chrysler called the almost identical design Sure-Grip, IH also used it as Twin Grip. All basically the same design.
