I've done some funky things with aircleaners. If you want to use the original (from the aftermarket aircleaner) filter media and cover, it's easier to make a mounting plate to match your S&S, and weld it to the aftermarket aircleaner backing plate. Grind it smooth, paint it black and it looks like it belongs there....
Another method is to cut the back out of the a backing plate that fits, and weld it into the one you want.