As NickR and spictacular said, it's probably the disty. The symptoms of a failing ignitor module (inside the distributor) are just that - it will stop working when it overheats, then start working again later.
Non-OEM distributor assemblies have also been known to fail sooner than the OEM units, which may explain why you are back here again?
The alternative is to do the HEI module replacment, which uses a standard, $20 GM ignitor module to replace this cheap, small one.
Last edited by schwinn; 4-5-05 at 12:29..