71 Dart Swinger wheel/tire combo suggestions

Measure twice. Biggest I can fit on my 72 scamp is 245. Leaves 1/2 on each side. Measure from the "contact points" the inner fender lip and the leaf spring. To the mounting surface on the axle. That will tell you your total possible width. Find a rim that takes that in half and you're on your way. Make sure you leave 1/2 on either side for side to side motion and what not.