Knocking

My wife was complaining that her '97 Tahoe (5.7 VIN R) was knocking and rattling under acceleration. I pulled the dist. cap and saw that the rotor was sparking at one edge of the contact. I was able to turn the dist enough so the knock went away. I figure the rotor position when the spark occured at advance was slightly too far ahead of the cap contact. She told me yesterday that it's starting to rattle again. The truck has 130,000 miles. I've heard horror stories about the distributor on these engines. Any suggestions?

Its not a horror story, it sounds like the dist. gear is worn.
Remove the dist, replace the gear and set the camshaft offset to 0 degrees at 1000 rpm.