What's the biggest front tire you can fit on a '73 Duster?

Well, after a trial fitment of a friend's set of 15x8 Mopar rims with 255/60-15 tires, I decided that those tires would work best. The new rims are 4-1/4" BS. I had my tire guy mount a 215/70-15 on the front and it hit the bottom front edge of the wheelwell. I had to go to a 205/65-15 0n the front and that cleared by about 1/2" ! (This was on a ARE Outlaw I 15x7" rim w/ 3-3/4" backspacing