275/45r18 on non duster anyone?

You can go up to 11.75 inch discs (Mopar cop car) and still stay with 15" wheels if that's what you prefer. Very nice upgrade. All it takes is a rotor and caliper bracket swap, and it bolts up to your existing spindle. If you can't source the parts locally, Dr. Diff carries them brand new.
As far as tires, there's still lots of choices out there in a 275/60-R15.
https://www.tirerack.com/tires/Tire...&rearRatio=40&rearDiameter=17&performance=ALL
https://www.performanceplustire.com/products/ts:275-60-15:ty:Tire/