So, 36s will definitely rub with anything like a stock wheelwell. Even with the modified wheelwells I had (larger than stock), 36s would rub.
My goal was to be able to run the 36" XZL (9.00R16) with no rubbing, even at full steering lock with the front suspension compressed.
To do that meant substantial modification, including taking the body mounts back and bringing the edge of the wheelwell (and rock slider) back to match.
The result was a truck with substantially more space for large tires that looks like it hasn't even been modified (awesome).
Here's the truck with the usual "body mount chop" and a 36" tire mounted. As you can see, this would have been a problem:
Just how much had to be cut and reinforced to fit these tires? A lot. This picture should give you an idea.
Surgery:
Test fit of heavy fill plate:
All stitched up:
As you can see here, contact with the rearward edge of the wheelwell (and mud flap, etc.) would have been inevitable with any degree of articulation in the rear:
Obviously, something had to be done... and the answer was to carefully trim and move the leading edge of the rear side of the rear wheelwell backward.
That looks like this:
Huge difference, but most people wouldn't spot it.