I called a few local municipalities after I found out no local oil change shop or filling stations would take old gas. I sure wasn't going to dump it anywhere. One municipality suggested contacting the fire department, thinking they may take it as hazardous waste. But no. However they were able to put me in touch with 2 EPA branches, who eventually gave two separate drop off centers, with the closest being around 50 miles away.
Old gas is hard to dispose of, and it took 7 or 8 phone calls to find a place.
What I learned, as big of a government entity the EPA is, I was surprised how little the local government agencies knew about hazardous waste disposal.
BTW , I reused the filler neck, and also the hold down ring for the sending unit. The new rings are not as thick, and I have heard they are prone to leaking because they can't be sealed as tight. FYI