Moved rear end back 1.5

I wasn't aware this was a popular "mod". Can you explain why you would want to do it?

So you can fit a decent diameter tire in the wheel well. Even after relocating the axle back it's still very restrictive unless you like the jacked up rear look.

I know that leaf spring Mopars weren't prone to wheel hop because they had such a short leaf section in front of the axle. Will the movement cause problems if you're going to drag race it?

No, the pin in the leaf doesn't move. The entire rear and springs move back 1.5"

How beneficial is it?

Well if you want a taller tire. It invaluable. There are only 2 ways to do it. Stretch the wells or move the rear back.

ain`t gonna help rear end weight. going to have the same effect as making the rear lighter, not good for traction !

Bullsh$t. It has very little effect on weight and it will not change the way it hooks at all. I take it you've never done this mod?

That's one of the reasons that I didn't do this one mine. I'm guessing you're losing the "Mopar leaf benefit" but I guess you can run Lakewood bars like the other guys then.

Again it has no effect on the placement of the axle on the spring. No measurable weight differences. No effect on hookup.

If you do this move you have to change the drive shaft right?

This is not a straight answer... It depends on a variety of factors. If you keep the same rear, probably unless the DS was very tight. If you do this mod and go from a 8.75 to a dana, no. Now, more trouble. If you go to a dana and run a performance cover you will have to do a little grinding on the cast rib. and you may have to dent or modify your tank.

The next thing to address the OP is the shocks are not an issue. They still get hooked up stock. 1.5" isn't much at all. You'll see that. Don't' move your rear shackles either. I assumed you need to. You don't.