Track width-wheels

[my56chevytruck]

This is not a what wheel to use, this is to discuss what SIZE and WIDTH of FRONT wheels can be used. I have the 56 chevy truck 2nd series, with a 2nd generation Camaro/Trans AM front suspension. The track width is 61", (measured from wheel mounting face to wheel mounting face). I'm wanting to know, what wheel Sizes and width CAN be used. I'm running upfront now 15x7 wheels with 215/70/15's tires now. The backspacing I'm getting is 4.25". I'm contemplating on going to new wheels but only find (in the style of wheel I like) 3.75" in the same size wheel. Also, I have 2" dropped spindles upfront and at times I've experienced wheel rub in while turning. I've removed some of the inner fender lip to minimize this problem. The picture of the wheel is the style I like; U.S. Mag Wheels

My good friend Mike Allen (slammed57 of this forum) suggested I consider a 15x6 wheels and to post my question on this forum to ask:

What size (width) wheels and backspacing are you running on comparable trucks.