Wally.....Thanks for that info. This "warm/no start" issue started back when the old starter/solenoid was on the truck. The starter/solenoid was replaced with new ones, and I still had the "warm/no start" problem. Also, the autoparts place tested the old starter and said it was still good.
As soon as I have time, Im gonna make a heat shield for the starter and see if that helps any. As someone said, as the headers get old (now 30 yrs old), they get thinner, and could be radiating more heat toward the starter/solenoid, which is only a couple inches away from the pipes.
