On a 1963-era Hamden door, we're almost always replacing a galvanized extension spring pair, not a torsion conversion - unless the door's already been upgraded at some point, which happens but isn't the default. We measure wire gauge, coil length, and the door's actual weight rather than matching the broken spring by eye, because a mismatched spring either over-lifts and slams the door open or under-lifts and leaves you hauling it by hand. We add or replace the safety cable through the spring if it's missing, since that's the one piece that keeps a snapped spring from becoming a projectile. Pulleys, stationary cones, and S-hooks on doors this age are usually original equipment and get swapped with the spring rather than left to fail next. We test the balance afterward by hand, not by the opener, so we know the springs are doing the lifting, not the motor.