235/60/15 on front of duster?

IF the 15x7’s are really 4.5” backspace, the 225/60/15 is the safest choice. The 4.5” vs. 4.25” backspace flat out gives you .25” more clearance.

Otherwise 235/60/15 is tempting on the 15x7 -4.5”. Does the 73 duster have a lower front fender support bar (usually attaches to hole on side bumper bracket)?? If so, you could lengthen that to push the fender out a little for additional clearance. Not sure how comfortable you are with that being new paint.