My 60s Renault had the fillercap under a centre locking panel at the rear of the car
There was some other stuff in there too
VW Bugs used to have the gas tank and cap under the front hood. Some also had an interesting accessory—a gas heater that tapped off the gas tank. This heater was required in cold climates as the aircooled engine heater put out about as much heat as a hamster blowing on a burned out match. Anyhow the gas heaters smelled bad and used more gasoline than the car engine did. Glad that one went away.
My uncle said it always heated up about the time you got where you were going - the regular bug that is. Karmann Ghia, I think his was. IIRC and it was a loooong time ago.
The really early ones didn't have a gas gauge. There was a lever on the floorboard right above the tunnel connected to a rod that went into the gas tank. It had an pair of open ended "cans" on the end of it (inside the tank). When you filled it up, that would fill up the top "can", and when it ran out of gas you flipped the lever and that dumped the gas in that can out into the tank, and turned the other can up. Then it was time to go find a gas station and fill it back up. You could easily get stranded driving on rough roads, because the bumps would slosh the gas out of the can, and when you flipped the lever, there was no gas.
My 60s Renault had the fillercap under a centre locking panel at the rear of the car
There was some other stuff in there too