440 with slant 6 torsion bars
i upgraded my slant bars to .890's with my slant and they are still soft...
All metal springs(valve, suspension, etc.), work harden in use. This means they, sag, lose spring rate and loose "resilliance". This is a quality that allows newer/stronger springs, to ride better. Best to compare shock valving while planning the car usage. As noted, KYB's(gas charged) shocks, tend to act like a little more spring rate.Just going to higher compression rate valving on shocks will help with marginal spring rates. True, 90/10 drag shocks woun't be much fun, on the street, but they'll sure feel like more spring rate. Putting more anti-dive, on the upper control arms, will tend to act like more spring rate, reduce bottoming over dips, and should improve cornering, with enhanced, "roll caster gain". Good Luck, ateam.:read2: