these are interesting threads because different trucks have different weaknesses and need different extras
I mostly travel hwy 5 and have done seattle area to San Diego a few times with other trips to central Cali.
For a long enough trip oil change supplies and try to keep tire change items on hand, like bottle jack and breaker bar. Otherwise just maybe a small socket set and spare fuses.
Really want to spend more time in Utah and Colorado but the 4.10 gears get painful on the freeway…
These are more day to day but I also try to keep consumables on hand like gloves, paper towels, funnel, oil, fuel additive, basic strap wrench etc