Not sure if this is known, there's a guy/company in Germany called C.Andy's who makes and sells adapters to fit 10th scale TC nitro wheels on WGT/Pro10 cars, for both front and rear wheels. Unfortunately the website is in German only. And I can't post URLs because I don't have sufficient posts. If you type the following in your favorite search engine the first hit will take you to the announcement on RedRC back in 2011:
"redrc c.andy's pan car wheel adapter"
The front wheel adapters are made from some type of plastic and should be pretty affordable. The rear wheel adapters are milled aluminum parts, probably a bit more expensive. I bought a pair of both front and rear a while ago when I was in Germany but haven't had a chance to use them (don't own a WGT/Pro10 right now). I don't remember the exact cost, but I can give him a call and ask, if there were interest in this.
I know the goal for this class is to eventually go to rubber tires, so this would seem as just another solution for foam tires (albeit with nitro wheels and these are quite cheap, less than 20$ for a set of 4 wheels).
I'm not familiar with the hex sizes of 10th scale TC nitro wheels and 10th scale electric TC wheels, but if they are the same then these adapters could possibly be used to fit 10th scale electric TC wheels with rubber tires onto WGT/Pro10 cars. That would be your rubber tire solution for people wanting to join in the class with those cars. No idea if those wheels will fit under the bodies discussed here, but that's for you to find out
I attached an image of my adapters where you can also see the rear ones.
I'll be at the 2014 Halloween Classics at NORCAR this year, I can bring these along for anyone to try them out on a WGT car. I won't sell them though :-)