Also 59 a posi was offered, and its different than the non posi. If its a spreader type case its the new posi, if its a drop out third member its the old non posi style, but I have one of them with a limited slip unit in it?
The Positraction option used a Spicer 45 (similar to a Spicer 44) sourced from the GMC side. '59 was the only year it was used in Chevrolet. The HO33 axle did have a Posi variant, but they didn't come out until '60, and were only made until '62.
