How to roll the rear quarter lip?

I’d use a heat gun for the paint no matter what. Heating it won’t hurt it, it will only help your cause. If it cracks you’re screwed.

The rollers you can buy are pretty self explanatory, and they’re not hard to use. The big thing to keep in mind is to go slow, don’t try to roll the thing in one pass. Just take a little bite and work it back and forth, then add a little more step by step. If you try to push it all in one pass the paint is more likely to crack and you’re more likely to mess up the bodywork.

With a mini-tub and full 3” relocation 325’s should be fairly easy with the proper backspace. I’ve seen 335’s on cars with that set up, I’m a little surprised you even have to roll the quarters for those.