I saw some at the Portland Or swap meet, they were very rough and expensive. I have seen guys make wide five 15s by removing the center from one, turning it down the welding it in a new 15" outer. 15" outers are easy find, you loose a lot of the openings around the edge. Since everyone here loves pictures and I feel I never have much to add I figured I would share one of my wide five experiences. A friend of mine wanted a set of wide fives that were wider than the stock ones wider so instead of splitting the wide five and adding in some strap we found some 16s that had the rite inside diameter and he carved-out the inners to leave just the outer. That was a lot of work, he had to carefully torch out as much of the center as possible then make grind the remaining down. He brought over a really cool shaft set-up he brought at the junk yard to make a truing rig and I cut off about 6" of the shaft, turned a step and drilled and tapped the end. I made a wide five mounting plate out of 3/4" thick aluminum and pressed it onto the shaft securing it with a bolt. He built a holder for a dial indicated to run on the bead surface to true up the outer. it worked pretty well, it is amazing how out of round and out of shape the donor wheels were. The donors were some late model wheels he picked up at a wheel shop that had the perfect inside diameter. I grabbed a set of my wide fives that had badly rusted outers and carefully drilled the rivets out and pressed out the good centers. I opened up the rivet holes so I would be able to get good plug welds to the new outer and cleaned off the rust on the mating surfaces. Once the offset was correct I started plug welding through the wide five rivet holes using a pattern like tightening lug nuts. it worked really well and the wheel stayed very true during all of the welding. I did not feel comfortable relying on just the plug welds, although they all had great penetration, so I welded the back side of each spoke too. I welded up and ground down the old valve stem hole because it ended up on the inside to get the desired offset and drilled a new one. He had them powder coated and runs them on his Ford two door sedan. The adapter is something I have been working on for a couple of years, he uses this early set on his sedan with factory wide fives up front and the widened set in back.
Many 50's oval track racers would widen 15" Buick wheels and use a wide five centers. I have three that were started but never finished.
Lots and lots of new, contemporary wide 5 racing wheels are 15". In fact, it's hard to get racing tires in anything bigger than 15" these days. Gary
Keep in mind that the modern racing wide five wheels are made for 5/8" studs and 45 degree lug nuts. Not saying you couldn't use them, just not buy and fly.