I have a section concrete roadway near me that is my proving grounds. The car follows the waves of concrete up and down with what feels like zero suspension movement. So I generally avoid this section of town. I put a zip tie on the shock shaft and drove that section of roadway. The zip was pushed up only 1/2 inch when I got home. I removed the front shocks completely, configured a stiff wire and loop for the zip tie and drove the same round trip. No perceptible difference in the ride and the same 1/2 of zip tie movement. It seems that the spring is loaded to a point where the spring rate ramps up considerably. While Bilstein shocks would allow more motion, there would need to be motion. Like others have pointed out, the spring needs attention. Removing a leaf or 2 AND re-arching the remaining leaves to get the static height back to or a little higher than current ride height and adding some clearance at the frame all seems a better first action. I'll working on that and with a potent SBC and TKX, I frequently drive the piss out of it.