Spacers aren't going to fix it, spacers will push the wheels out further and make it much worse. Going more positive on the wheel offset won't help either because it's going to rub on the UCA's and other areas on the inside. The tires are too big for the current application.
EDIT: Actually this guy has a similar setup to yours and fixed his rubbing issues and made a how to thread.
Snapped some pictures while modifying the wheel wells today to fit my 35x12.50x20 on a 20x10 -18 offset. Lift kit is a ReadyLift 3.5 SST A lot of people ask do they Rub? Answer is Yes, solution is easy since it’s minimal labor. Tools needed: Wet towel 8mm socket Grinder Spray paint Heatgun...
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