I bought some really bad regular gasoline in the summer (August after 12.00 noon) of 1980 in Barstow, CA on the way to Las Vegas for a bracket race from a cheapo station, it was horrible on vapor locking, I ended up tying a rag around the gas line from the mechanical fuel pump up to the carb and sprayed it with water from my garden sprayer that I used to cool down the race car radiator between rounds. It would go about 5 miles and start vapor locking again That was a 1957 Dodge one ton truck with a race car hauler ramp and storage compartment with a later model Poly 318 motor in it.
That started at the bottom of the Baker grade on Hwy 15, that grade is right at 17 miles long to the top
A old timer told me later to take wood clothes pins and put them on the gas line to the carb.help keep it cool, that work very well