The pedal height is controlled by the rear brakes. I would adjust them a little tighter and see if the pedal height improves.
if the drums are worn out (above max o.d.), you are going to need to replace the drums.
You should have the Kelsey-Hayes RWAL on that truck
http://www.aa1car.com/library/abs_kelseyhayes_rwal.htm unless the C1500 is different.
You may need to bleed the Electro Hydraulic valve or it might be bad.
//2000CAYukon