Gasoline has a thermal expansion rate that is over 4.5 times that of water! That is why the problem seems so dramatic. Gas expands a lot.
You could always add an overflow tube to the filler neck: Remove the neck, add an overflow tube, reinstall the neck and pipe the overflow out of the cab
Or just don't fill it up all the way.
As a kid, on the farm, I used to be assigned the task of filling up the old mans '72 Chevy C20 with gas when he got home from work. I got to where I could tell by the sound when the gas got to the filler neck it was time to stop.
If I overfilled it I got a boot to the butt! Ahh the art of positive reinforcement. It's an aquired skill.
John
