Fuel pump parked up hill

The best thing I did --V8-- before going to EFI, concerning hot weather, vapor lock and other related fuel issues was to............

Go to rear mount electric pump. I found an almost new "Red" pump at a good price

Constructed a vapor return system using a Wix 33040/ 33041 filter, which has a built in return port.

Added a thick 3/8" carb isolator under the carb.

If your car has the evaporative system "carbon can" it might be malfunctioning and causing a "no vent" situation

As said, might have pinholes in the feed line.

The "usual suspects," collapsing connnector hoses, partially plugged tank sock, or weak pump,

There are procedures in the shop manuals to check the pump for suction vacuum, output pressure and for volume.