hard to fill with gas

[mar-tay]

I've got a 1974 longbed and it takes forever to fill the tanks (2) Both are 20 gal factory tanks and when I try to fill them the gas splashes back and onto the ground. I have had the tanks out, replaced all of the hoses (vent hoses too) and the only way to fill it is to go really really slow. I'm here in California where they are constantly messing with the pumps, as some seem to work OK when I get out of the area (rural places). Any ideas? Anyone else had this problem? Thanks