Landrum does leaf springs. Haven't talked to anyone at Calvert. Someone should be able to build a spring to spec.

Spring rate and compression at ride height. I'm not an expert but a low rate spring with enough arch to get it loaded and hold desired ride height will store more energy than a high rate spring that is deflected less..

More horsepower, gear, etc usually means less help needed from low rate springs to get the tire applied. i.e same car, same weight with a mild small block and automatic would get a different spring than a decent big block stick combo. Springs matter. They don't just hold the car up as some people think.