For a call in Normandy Park, the truck carries what a 1960s-built door actually needs, not just what a modern one does: replacement brackets sized for older stud spacing, track sections in the lengths that match pre-1980s door heights, and rollers in both the nylon and steel options, since we won't know which one the house was last fitted with until the door's off the rail.
We also carry spring tension bars and clamps, since freeing a door that's jumped track means killing the spring load safely before anyone touches the panel - that's not optional and it's not something to improvise with a ladder and a pair of pliers.
What we don't carry is a guess. If a bracket or track section on-site turns out to be a size we don't have loaded, we'd rather say so and come back with the right part than force a fit that won't hold through the next cold snap. Tukwila Garage Door Pros runs this call from Tukwila, about 4 miles out, and the truck is stocked for the housing stock we'll actually find on the way there.