I have been building rear ends for 60 years and I am thoroughly confused at what you are trying to do. It looks like you have the GM corporate HO33 which was later called the HO35. There were only two gearsets available for these. The GM 3747808 which is a 3.90 and later the 3764960 was available for auto trans at 3.38. I would be interested in seeing what you bought and what you are going to do with it.