Vapor Lock On A Beautiful NW Summer Day

I don't know if this helps, but it cost you nothing...and sometimes you "get what you paid for".
An old friend (Corvette guy) offered to look at my 66 Coronet, that was having a similar sounding issue. His conclusion was that the fuel was boiling, or close to boiling in the carb. Today's unleaded fuel has a lower boiling point, so I'm told...about 185 degrees. While he tweaked a few a few other things, he said that the most dramatic change came from the thermal insulating spacer that was added between the carburetor and manifold.

Good luck