The limited slip rear used was a spicer 45. The HO33 was likely to be the rear used in a 57. The HO33 does not have positraction or limited slip setups available for it. There are also only 2 gearsets you will find for it... 3.90 or 3.38. If posi traction or limited slip is a requirement for you... you will likely have to find another axle.

It was a priority for me in my 1940 gmc, so I ordered an IMCA modified ford 9 inch. You can get them in any width, bolt pattern, and strength you can imagine. Not to mention it has a virtually infinite sellection of gears, positractions and limited slips available for it. Best of all it was all new, and I didn't have to crawl under a bunch of trucks at the wrecking yards with a tape measure to find one.