these are 19.5 wheels from a P30 stepvan with 8R19.5 tires
http://rides.webshots.com/photo/2620734620106850169lkHiphstock 3800 suspension no clearance issues. 7.50-17, 7.00-18 & 8R19.5 tires are all very close to the same height. I've got some of the old 18" multi-piece wheels. I took the center out of one to see if it would go in one of my 19.5 rims. sadly it was about 3/16-1/4" too big. I'm going to put some mold release wax on a rim & lay some fiberglass on it to make a pattern where I can make 4 more holes in the wheel center using hole saws. An 1 & 1/4" for the ends & About a 3" for the middle will reproduce the oval hole in my rims with 4 little ears left to clean up with a die grinder. I'll document with pics when I do it & I'm sure I can get them close enough the wheel will balance fine.