The cone type sure grip has a much larger pinion shaft block, instead of the sure grip thrust pin. I know that with the early tapered rears and the 1965 flange 8 3/4s, there were TWO pairs of possible axles. Non sure grip and cone type sure grip and then the clutch type sure grip. They both varied a little in length and were not interchangeable, because of the thrust block, thrust pin. Now whether that's true for the later 8 3/4s, I am not sure. If it's not, then it sounds like you may have a pair of early axles in a late model housing. I have had to trim axle ends off before with a miter saw to make them work. If you do that, you'll need to dress the edges of the splines so that they will slide into the side gears easily.
