I’ve got a 2020 AT4HD 2500 with the Duramax and love it! From all I’ve seen you can fit 35’s on the stock wheels without doing anything extra. If you plan to switch wheels you’ll run into some issues. I’m currently waiting on new wheels and 35x12.5x20 Ridge Grapplers to put on in conjunction with a Kryptonite Stage 3 leveling kit, only raises it 2” in the front, I already installed a set of Air Lift Ultimate 5000 air bags that take of any squat so truck should stay level the whole time I’m hoping. I tow a 37’ ~13,000lb RV so hoping my combo works out with no issues. Sent from my iPhone using Tapatalk