What finally fixt it? My neighbor.
Carburated '67 ford truck. Intermittently would start fine, or not, but "not" quite often once was warmed up. Unfortunately, while can follow a shop manual am not otherwise a mechanic. Gave truck to TWO local mechanics, the second guy asked him to keep/drive it for the week. Couldn't find anything wrong...
Pull in driveway getting home from the second shop, pop the hood, poking around looking for inspiration when my neighbor buddy walks over. He's not a mechanic either, but he's tinkered on his GTO and others for years. So share with him what's been happening.
"Fuel or ignition, you think?"
"Fuel," I say.
"You got a minute? Let's just start simple and see." Sure, what the hell, right?
Sprays some carb cleaner around, low and behold the two gaskets (spacer) below carb and a third, the carb's top cover all leaked like sieves, in part because most fasteners were between loose and not-tight. Cleaned/replaced/tightened them up? Fixed.
Took a knowledgeable shade-tree mechanic neighbor one minute to find what two free-standing shops couldn't in a week and a half?. Blows the mind. At least I learned something.