Nobody has mentioned overall width. Won't the B-body axle push the rear wheels further out in the wells? This could be an issue with wide wheels -- you would need wheels with more backspace.
Yup, the B body rear end will push the wheels further out. Since the OP is talking about a Duster though it isn't as much of an issue, the stock 7.25" rear was significantly narrower than the front track width. It could be a problem if he's running aftermarket wheels with very little backspacing, but based on the pictures at the top of the thread the wheels appear to be some kind of OE steel wheel with the tires right up against the springs. When I switched my car over I was running 15x7" mopar cop wheels with a 4.25" backspace and 225/60/15's, I didn't have any issues with the wheels fitting. They were about as far to the outside of the wheel well as they could be, but they didn't rub.
Of course there are several different B body axle widths with a 44" spring perch, but I'm running the 68-70 B rear which is the widest of the group with 44" spring perches. If he's got a 65-67 B rear it would be a bit narrower and give a little more room. Now, if he wanted to really max out the tire width the backspace would have to increase compared to the stock wheels.