A door built to a 1974 rough opening doesn't always take a modern spring or a modern opener bracket without some adapting. The stud spacing, the header height, and the track drop on houses from that build year are close enough to today's standard that most repairs go straight in, but not identical - we've had to shim brackets and swap end bearing plates on doors where the original hardware was installed before torsion springs were standardized the way they are now.
Cold makes the second complication. In this climate band, steel spring wire loses tensile give as temperatures drop, and a spring that's already fatigued from forty-plus winters is the one that lets go on the coldest morning of the year, not the mildest. That's not a coincidence you can plan around, but it is a reason we see more snapped-spring calls out of Auburn in January than in July.