For a standard install we carry sectional steel door panels in the common widths, torsion springs sized by door weight, galvanized track, rollers, and the cable and drum hardware that goes with a torsion system - the same core components regardless of house age, but sized differently for a wider early-90s bay than for an older single-car opening. We stock standard openers and the sensor and rail hardware that go with them.
What we don't carry as standard stock: glass-insert panels, custom paint-matched finishes, or oversized triple-door units built to a nonstandard width. Those get ordered once we've confirmed measurements on site, which is the one part of this job that can't be rushed - building it to the wrong width means redoing the spring calculation from scratch. Given the mild temperate climate here, we're not building in the insulation or weatherproofing margins that a harsher climate would call for, which keeps material choice simpler than it would be elsewhere.