73 dart...B body 8.75...what size wheel/tire

...........I have a rear out of a 68 road runner in my 74 duster.........my rims are 15x10 in wide centerlines with 5in back space.....have p295/50r15 gy eagle gt2s........i have 1 3/4 in to my springs from the tire buldge.......my tires stick out about an inch, so 6in bs would be better on my car.......kim........

Sure sounds about right that you need 6" BS because a Wheel Vintiques Mopar reproduction 15x10 wheel is 5.5" BS as a 'mass production' aftermarket wheel, and your B housing is wider than an A.