With roughly 2,372 households and a median income near $84,583, this is a area where owners tend to fix rather than replace on the first sign of trouble, and the housing stock backs that up. A door installed in 1976 has likely had at least one torsion conversion or opener swap since, sometimes done well, sometimes done as a quick patch by whoever owned the house before. We see mismatched springs on doors that were clearly upgraded once and never rebalanced properly. It's worth having someone check the spring size against the door weight if you're not sure what's on there now - a spring rated for the original panel material won't sit right if the door was ever replaced with a heavier insulated one.