Here is some additional information about the other potential option. The current carrier in the 8.5 is a veerryyy tall gear at 2.41 so the series of the carrier is not usable for my desired 3.73, 3.90, or 4.11 gearing. The casting on this 8.5 housing was very difficult to read but it appears to be "PS G63038". This is a GM rear end with c clips but I would be replacing the carrier with a BOP unit from the picture above so I could use my BOP axles if I went that route. I just cannot figure out how to tell the differences when the housings and pinion gears for each carrier are not available. The bearings mic'd out the same, the ring gears had a similar fit, and the 28 spline BOP axles fit with all of these units.

Here are the two rear ends. The original rear end from my bird is on the right.


Here is the 8.5 posi unit that I purchased last week. (I didnt know the differences or what to pay attention to like I know now)


Here is the casting from the middle posi carrier that I compared to my open carrier in the last post.