Last week I found what I thought to be a great deal on 5 buick rally wheels with tires on Facebook Marketplace. I am rebuilding a 1971 Skylark and wanted to change the wheels from the original 14x6 with hubcaps to 15x7 rallies. After I brought them home, I realized there were two different bolt patterns for the rally wheels. One is the mid size GM (5x4.75") and the other is the full size (5x5"). I bought 5 of the 5x5". The rear axle looks to be a BOP 10 bolt with the bolted in axles, not a C clip retainer. I went looking for the code stamp on the axle housing but it wasnt there. I am assuming its a BOP not Corporate based on the retaining plates and the diff cover that has scallops on each side. Plus the axle flange has access holes to reach the bolts on the housing so redrilling the axles for the new size wont work. I plan on changing the fronts from drum to disc, to I can redrill those, but it seems like I can't get new axles on the rear with a 5x5 pattern and the provisions for the BOP bearings. What are my options here? I can do alot of the work myself, but it seems like I am about to open an entire can of worms if I decide to change the bolt pattern.