opening the rear wheelwells for larger tires

You're defeating the purpose of Super Stock springs by doing that, but some folks do it. Your car, your taste. Long shackles are one of the worst things you can do on a Mopar. They make the rear suspension unstable, because they make more room between the frame and leaf springs. That gives the springs more leverage to do some nasty things. Like bend the shackles. You need to take those off. The 1" further back thing is ok, but not optimal. Make sure your drive shaft has enough engagement room. I know it's "only an inch" but I've seen it make a difference. For the bad. A 33" tall tire" Time to back half it.