Fuel Tank Question: '60 Val

I see what looks like a small vent port on the filler end. Maybe the leak was there (the hose) since you filled the neck and pipe at the station.
I'd also pull the sender and clean the o ring seat area well.

If you can't find any problems, put it back in, leave the car raised for easy access to inspect, and refill. Add a little at a time until you see a leak and trace it back to the source. Blotting with paper (versus a wet finger) will make it easier to trace. Home Depot has an orange siphon hand pump for about $20 that can be extended with clear hose over the pumps hose. They is also a "jiggler" check valve siphon that can be found online, but I found the orange pump adequate.