Some people, new to old trucks, think everything they just learned is a new trick. Old trucks, old engines and how to fix and operate them does not change. Computer operating systems do. If you ask for help, you are asking for an opinion. Opinions can also be facts. They can come from trying "new tricks" years ago. From actually being in the automotive trade. From being around long enough to know what works. What works is not half [censored]ed. Feelings are hurt by those who thought they were answering. Generally all forums are like that sometimes. Older people hear that "teach an old dog new trick" thing all the time. It's just a cheap shot at knowledge. You can't teach a wrong idea to knowledge.
The Chevy 350 motor plug gap started as high as .060 in mid 70's and has bounced between .035-.045 up into the 90's. All HEI. The auto makers have tried as high as .080 and came back down. Many years of .035 gap for 350 Cu In. HEI. This is with variations of systems like carbs, TBI, TPI, MAF, etc. and plug design improvements. .035 is an old "trick" and all the new dogs use it.
Bottom line: The U.S. Constitution says: "All persons shall have the right to set their spark plug gap to any dimension and Congress shall pass no law to remove this right"
My gap info, for what it's worth, comes from checking Chevy 350 motor from 1974 to 1994.
