Well, that's both good and bad news I suppose. I guess I'm relieved. Vapor lock seems to be one of those things you can't really control.
As long as I'm replacing the pump anyway, has anyone tried the trick of using a 455 SD (73-74?) fuel pump? I don't remember where I read about it (maybe on this site), but it supposedly has a larger fuel bowl. The downside is, you have to get the SD fuel line as well.