I can now 100% confirm that this specific wheel/tire setup WILL RUB regardless of using a heat gun on plastic. I will need to remove the plastic to expose the metal underneath and trim about 1/4” off, then it will be good to go.
Foutz collars 1.5” front only
20x10 -18 offset wheel
Nitto Ridge Grappler 37x12.50x20
Rubs ONLY on the rear sides of the tire (closer side toward rear of vehicle) right where the bottom most bolt is located. Only hits it on a hard turn left or right on each side, otherwise it hits nothing else.
Not a big deal. It looks badass.