69 Dart rearend

I'm starting from the back and working forward on my build and am curious about the same thing. I've got a 70 Swinger I'm planning to put a Level 3 US Car Tool kit on. That kit looks to be a 3" tub and the springs are moved in board / under the rails. Seeing that Strange has a sale on complete rear ends and free freight right now, I got a little overzealous with my day dreaming and almost spent my entire budget for the year on something that might not have worked at all, haha. Either way, got me thinking about this same question, but for a 70.

How wide a tire can you fit now? Sidewall to sidewall? I'm thinking I may have to radius my wheel wells too.