I got home the other day...hit the garage door opener, and was overwhelmed by the smell of gas. Gas was coming out of the gas tank neck and running down the side of the truck.............
grabbed a hose and syphoned off some gas (i had filled the tank for the winter....added some Heet and Sta-bil).....now THAT was a taste treat....took me back a few years to another time, but that's another story
It sounds like it was cold when you filled it then after being in the garage it warmed up and expanded causing it to overflow.
I have had that happen before. I try not to fill it to the brim anymore. It is amazing how much that stuff will expand!! My '60 isn't quite up for the year yet. It is parked in the shop where I work on it when I get the chance. Hope to get at least another good spin before the white stuff comes to stay and the road crews start to throw the evil white stuff on it to make it melt.