[Bill Eveland]

The last one I took apart , the pinion lost every bit of gear on it. This was just in a stock s-10 Blazer 4wd. I think they got stuck in the snow.
Don't waste your money on the 7.5.
The 69 12 bolt is about 3" wider, if your buying axles anyway, go with the 12 bolt aand have the housing narrowed or a bolt in g-body 9" housing. If your buying axles anyway that would be a great time to get the Moser axle ends that use the ford big bearing ends and stock gm brakes. The backing plate will have to be opened up for the bigger bearing.
South side machine lift used to have lower control arms to mount the older 10/12 bolts into a G-body.
Another friend of mine did something similar to what Colin was talking and used a rearend from a 68-74ish Nova and welded the backets on the housing. The brackets are available from some of the stock car building websites.