The fact is modern ethanol fuels raise what is called the RVP. Meaning, they vapor lock/ boil "worser."
Best things I did for my 67..........
Finally converted it to EFI
But BEFORE THAT
Abandoned mechanical pump, installed rear mount electric pump
Constructed vapor return system using an orifice fuel filter, AKA Wix 33040 / 33041
Added carb heat spacer. I used a 3/8" I think. Bought locally at O'Reallys
The vapor return systems were first used in the factory 440 and hemi cars, not sure just when, sometime in the 60's. First one I ever saw or had was on my 70 V code RR. IT WORKED
"The usual stuff"
Pay attention to fuel line routing, consider new hi tech sleeve insulation for the purpose
Some carbs, EG Ed AFB, are worse because the fuel bowls are in contact with the hot manifold surface
Consider blocking the carb heat crossover
Make sure the engine isn't overheating. Can the engine temp be improved?
It's ALWAYS possible you just plain have something wrong in the fuel system, IE plugged vent, weak fuel pump, pinhole leaks in the supply tube, or whatever. How old? again? are these girls?