Those are the 315's on the back huh? They fit better than I though they would. Although based on those pictures I don't think you could lower the car 2-3" and still clear. Take a look at the pictures of my 295's. It looks like there's still a ton of room from these angles...
But there ISN'T. Using a straight edge on the face of the tire, there's only about a 1/2" to the quarter lip, which is cut back a 1/2" already on my car. And then of course there's the "bump" in the wheel well, so there's even less room than that if the tire travels up into the wheel well.
But that's right now. The B-body rear is going to push your wheels another 3/4" outboard of where they are NOW. Which will put them entirely outside of the quarters.
What you actually need is a rear end the same width as the one you have now, but with the 1/2" spring relocation. I know, Mopar calls it a 3/4" relocation. Weld the perches wherever you like, but the hangers only move a 1/2" in. I know, they're on my car right now. It's a 1/2" offset. And it's a moot point anyway, because your tires will hit the inner wheel well before the springs with that offset anyway. Mine did before I added the rear sway bar to take out the rest of the body roll.