Want to go Bigger!

Hola all! I have a 74 Duster stock 8.25 rear. I am going to get a new set of leaf springs +1 inch over stock and I am looking to get some wider wheels and tires for the rear. I am wanting to go with Cragar SS mags. What is the widest that would fit this application without rubbing? The leaf springs are in the original location. Not relocated. What back spacing and width am I looking for? Thanks guys.

J