Hi All, this is just an FYI for anyone who runs into this problem. I was running 37" MTRs on 15" wheels with 2.5" backspace. As you know, you can hardly find a 37" tire for a 15" wheel without breaking the bank on Swampers or something. I called Summit Racing and spoke to Thad in the wheel dept...he was able to get a custom build on 17x8 with 2.5" backspacing for me at about $125/wheel. Hope this helps someone in my same position...good luck.