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

Need to look at the tire section width (SW) side wall to side wall Tire Rack is a good source to find this information just look at the specs for any given size it will then bring up every size available for that brand you can use your tire - wheel for reference distance from side wall to leaf spring - quarter panel lip but you need to look at the suggested wheel width on the tire specs there's someplace to figure the change in SW if your wheel width is different than the size suggested do the same for the OD I have done this several times and can get down to fractions of clearance never failed lets say your tire has a SW of 8" and the closest your are to either side is 1" times this by 2 so you could be a little under 10" on the SW