Widest tire on 8 3/4 rearend - 1972 Dodge Dart Swinger

Several have said 225/60/r15's fit well on front and back on a stock set up... I recommend going up to 15 inch wheels, mine are still smallbolt...

Here is a Cooper Cobra tire spec page, just click specs button...

Cooper Tire & Rubber Company - Cobra Radial G/T™