If you have a wood and metal shop you could design and build a visible gas pump, like DB suggested, get the art department to make the signs,.that way you can make everything to match... make it an all-school project.
I'm sure there are plenty of old pics in members hands so you could determine what signs would go with what brand.....gas,tires batteries etc. You wouldn't want Gulf maps in a Standard Station.
Maybe paint/design signs using your own artwork in school colors using the mascot as a brand?