I have 18" tires, 275 X 65R 18, Load 116T, actually a 5 Ply tire: 2 steel/2 poly/1 polymer bands. My truck is a DT Truck, 5th Gen Truck.
Per Falken:
20" Tires:
28034021 275/55R20 XL 6 117T 7.5 - 9.5 8.5 31.9 11.1 661 13 48.1 2833 50 660-A-B
28034003 275/60R20 SL 4 115T 7.5 - 9.5 8.0 33.1 10.8 640 13 47.8 2679 51 660-A-B
28030128 LT265/60R20 E 10 121/118S 7.5 - 9.5 8.0 32.5 10.2 640 17 58.2 3195 / 2910 80 -
28030008 LT275/55R20 D 8 115/112S 7.5 - 9.5 8.5 31.9 10.9 662 18 56.4 2680 / 2470 65 - New
28030009 LT275/60R20 D 8 119/116S 7.5 - 9.5 8.0 33.0 11 641 18 58.2 3000 / 2755 65 - New
28030120 LT275/65R20 E 10 126/123S 7.5 - 9.5 8.0 34.1 10.6 611 18 66.1 3750 / 3415 80 -
28034121 LT285/55R20 E 10 122/119T 8.0 - 10.0 9.0 32.4 11.2 642 18 58.2 3305 / 3000 80 -
28037329 LT285/60R20 E 10 125/122R 8.0 - 10.0 8.5 33.5 11.4 622 18 65.5 3640 / 3305 80 -
28037326 LT285/65R20 E 10 127/124R 8.0 - 10.0 8.5 34.6 11.4 603 18 67.7 3860 / 3525 80 -
28037328 LT295/60R20 E 10 126/123R 8.0 - 10.0 8.5 33.9 11.7 614 18 69.4 3750 / 3415 80 -
28030385 LT305/55R20 F 12 125/122S 8.5 - 11.0 9.5 33.2 12.5 626 18 66.1 3640 / 3305 80 -
28030125 LT325/60R20 E 10 126/123S 9.0 - 12.0 9.5 35.4 12.8 591 19 83.8 3750 / 3415 65 -
28037307 35x12.50R20LT F 12 125R 8.5 - 11.0 10.0 34.6 12.7 603 19 76 3640 80 -
28037331 37x12.50R20LT E 10 126R 8.5 - 11.0 10.0 36.5 13.0 570 19 77.8 3750 65 -
https://www.falkentire.com/tires/light-truck-suv-cuv-tires/wildpeaka/t3w-tire
They have Rated tires: SL (C), D, E, F, XL for 20". U just have to research and see what U want and check what is available/or can be ordered from your area and fit your rims/wheel well with proper clearance: I actually got my Tires from RAM Dealer: Buy 3, 4th Free.