And here are the results:

I took an AW hub and swapped out the standard driver and 5 3/4" axle for a threaded driver and 6 1/4" axle:



I then added a SunTour Perfect 8.8.8 5-speed freewheel, a spacer, and a locknut:



Installation is on my '73 Raleigh SuperCourse with 120mm rear spacing. I was worried that I didn't have enough axle protruding from the drive side AND that I wouldn't have enough clearance for the chain, but I think it might work:





Add derailleur, cable, and chain, and, voila, 15-speeds! I'm not going to try that with this SuperCourse as I have it currently set up with an S-A S5 hub though I suppose a 5 x 5 = 25-speed isn't out of the question! I must be channeling Sheldon Brown today.