We stock torsion springs across the size range that fits doors built through the 1960s and 70s, since that's most of what we see across this side of the metro, along with standard-width cable, rollers, and hinges sized for steel one-piece and sectional doors from that era. We carry universal opener logic boards and drive units that cover most chain and belt drives still in service on houses this age.
What we don't carry is a stock of parts for openers that were already discontinued when they were installed, or for custom door sizes cut for an unusual opening. On a job like that, we'll diagnose on site, tell you exactly what's needed, and order it rather than guess.
Given the cold-moderate climate here, we also carry weatherstrip and bottom seal stock sized for standard openings, since seals on doors this old have usually hardened and cracked from decades of temperature swings, letting in more draft than the door itself would suggest.