Widest Tire on 74 Valiant With Jeep Steel Wheels?

[bordin34]

I am buying some wheels from a buddy cheap and want to put them on my 74 Valiant. The wheels are from a 2001 Jeep Cherokee sport and are 15x7 with 5.25" backspacing. How wide of a tire can I fit under my car with out rubbing. I wouldn't be opposed to running a small spacer if necessary to bring the backspacing down.