I'm not near the axles right now. From your provided (very informative) picture I believe that they appear to be A-body sbp axles that have 2 sets of holes in the flanges. Would they be aftermarket?
If they have 2 sets of holes in the flanges they're probably not aftermarket. The aftermarket axles I'm familiar with typically only have once set of holes for the 5x4.5" pattern but still have the SBP offset, which is why they can be tricky. If there's two sets of holes they're probably just factory axles someone re-drilled. But I suppose they might also be re-drilled aftermarket axles.
Either way you'll have to confirm the flange offset, since it can only be right for one of those patterns.
