Hi ,have a 1999 C1500 2 wheel drive Suburban. Truck has 130,000 miles on it. i am thinking of changing the front springs as she feels like she bottoms out on the highway when I hit highway bumps at 60MPH and above causing a rough ride. I have 2 brand new shocks I will install also. Should I just buy factory standard springs or can I install a stiffer spring if available? Thanks for any input.