Falken AT3/W or Yokohama Geolandar X-At. Currently running Falken’s and they’re by far my favorite tire I’ve had so far. Yokohama’s will most likely be next depending on how well the Falken’s do.
Also, Gen 1’s never came with KO2’s as they weren’t made yet. They ran the original BFG AT that were actually good. KO2’s are too soft and don’t last. Burned through 3 pairs in 100K on my F-150, but I was comfortable and didn’t want to stray from what I knew on that truck. I experienced a similar situation with the Toyo AT II’s that came on my Gen 1.