"Newc" is correct; you can either make or buy 15" wide fives in just about any width and offset you desire. My vintage modified in the attached pictures has 15" wide fives all around. The rears are special racing units, but the fronts are 15X5's from a company called "Bassett", I believe. I have also made my own wheels for this car using centers and shells from Speedway Motors. It's pretty easy if you have a welder and a dial indicator. I'm sorry that I didn't fully understand your initial question.
(Sorry about the engine, fellas!)