Car stalling at idle after topping it off.

The alky-ized fuel is much worse for fuel boiling. One of the best things I did with my 67 was to build a vapor return system and use a carb insulator. I used a rear mount electric pump and ditched mechanical. You can buy fuel filters with built in return orifices. The hardest part is getting back into the tank. I temp connected the tank vent tube to a "high" outlet tube and plumbed CO2 from my MIG welder into the feed tube. Let it flow for a considerable time. I could light off the fumes being forced out of the temporary vent tube. When you could no longer light them, I knew the fumes were being displaced. I let the CO2 flow for several minutes longer, then punched (not drilled) a hole in the tank near the sender, and silver brazed a piece of tube in the hole for the return.

The best thing I did after that was go with EFI