Lowered 72,needs stiffer shocks and springs

[hesaw00]

Hey, looking for some direction.
I bought a 72 c10 several months ago. It was already lowered. Seems to have been properly lowered....drop spindles in front, no evidence of cut springs, etc. and the truck drives great....except that the shock/springs are really soft. Front tires scrub if I hit larger dips at highway speeds. How do I determine how much my truck is lowered? And what length of springs/shocks I should use as replacements? My main objectives are to get improved handling and no bottoming out. My guess is that I have a 3/5 drop. Thanks for any suggestions