73 Duster help .

I have on my 73 Duster 225-70-15 on the front and 275-60-15 on the back
On Factory 15x7 aluminium wheels with a 4 1/4 backspace and 1/4 inch spacer so tire dont rub the front spring clamp. May step up to a 3/4 inch spacer to bring closer to 1/4 panel