I have dealer experience from back in the day with my 73 240Z. Bought in July 1973 in SLC, UT. It was fine that summer. Over the winter I drove a bunch to both Denver and Albuquerque multiple times. Seems like the next summer is when I had my first vapor lock, more like a loss of power, like 25 to 30 percent, very noticeable but it still ran. I could always start it after being parked, but it would take some cranking. Took it in multiple times. They put on the fuel rail insulation, that didn't really help. They added the electric fuel pump, helped a little. On hot days on the way home from work I'd pop the hood latch like mentioned before. It would help some, always got me home. They fiddled with the flat tops a bunch, but never hinted that the carbs sould be swapped for round tops. It was pretty much like that the rest of the ~20 years I drove it. Other than the really hot days in July and August the flat tops were fine for over 100,000 miles.
Wilkes