First get a timing ligt and clean off your haromonic balancer. Mark "0" with some white out. Check the timing b4 you try to adjust it. Base timing on our trucks is 10 degrees. Try 14 degrees and see how that works.(no ping at higher rpm) Loosen the bolt at the bottom of the ditributor to do this. then you can turn your distributor. I cant remember which way is advance and which way is retard but keep the timing light on it and move it. Hope this helps.
Jason N.
95 Red #225