Aluminum small bolt Indy slot mags

The more backspace the better, to a point. That is the problem with the older mag wheels, not enough backspace puts the tire too close to the fender. 14 or 15 by six, with a 3 1/2 bs will probably work, cause you can't put a very wide tire on a six. 3 1/2 bs with a seven will likely also restrict tire size.
As said above , 4" or more of bs is preferred.