37X13.5-20 will need spacers to get the truck stance "right" as the wider fenders leave 1-2" too much room...
Damn up to 37's. I have the A/T II's, wanted the R/T's but back order was too long. Stayed at stock rim size 17' and went a touch smaller on diameter and width, but these are my winter tires so wanted be able to put chains on them, no lift. Went with a new rim though to get the added offset to make sure I had room for chains. Think I did the Fuel Anza's. I know I've read this but I can't recall where but from memory the offset total should be no more than 6/-6 or 0.....maybe you know or someone else will chime in. I know I stayed within 'acceptable' range.
A/T II's have been good so far in ice/snow/mud and dry. Just too damn stiff. Tire is a bit easier to spin as well, but to be expected since narrower and smaller. The BFG's are a much smoother ride on and off road. A/T II's are much better after I aired them down, but still not as smooth as the stock BFG's. First time off road with the A/T II's didn't go a mile and jumped out and aired them down the ride was so rough, was on the same road the week before with the BFG's and BFG's I never aired down..