It’s not possible to upgrade the valves, just look for a 2022 or newer.
At lower elevation the 6.0 HO will move that boat fine. If you ride with a big crew or run lead, or plan on going up in elevation Id go ZZ6, keep in mind the ZZ6 will be the more desirable mill and better for resale down the road.
2907 prop or similar will be necessary with the 6.0.