We put them on our 67 coronet after switching from stock to super stock , to the complete cal-vert set up, mono/shocks etc.
The car is weight is 37-3850 dep on driver, we didn't pick up any 60, in fact we lost a little, but the car did go straighter,but developed that bounce after the leave, so now we are now working on the front of the car to see what or anything is the issue, we put new 90/10 race shocks that was recommended by cal-vert , ball joints, tie rods , with no help. now we have to wait n see for the track to open to try some new items different setup on camber/ caster torsion bar settings.
But at this time, money spent over the ss springs wasn't worth the effert and the end results, at this time, maybe after much trial/ error sessions, maybe we can get more out of the system,