Classic/Antique Car Repair: Fuel Odor 1966 Rambler (corrected email address), overflow tube, gas gauge

Question
I have a 1966 Rambler Classic 770 4-door sedan.  It has a 232 engine. There is a fuel odor in the cabin that I can smell when I am driving.  I have replaced the rubber gas tank filler neck, the overflow tube, and all rubber gas line  tubing from the tank to the carburetor.  All rubber parts of the vapor tube have also been replaced.  I have installed a new original fuel pump and a new original 2bbl Carter WCD carburetor.  The gas cap seal has been replaced.  There are no visible leaks anywhere.  I can detect vapors coming from the overflow tube (the tube that comes out from the side of the filler neck).  This tube extends down behind the rear wheel well on the driver's side.  Perhaps this is not where the tube should be going?  When I replaced the one that was on the car when I bought it (6 months ago) I positioned it where the original one was but I am not sure if that one was even in the right place.  Maybe it needs to be extended?  It may not be the source of the odor but I can't seem to think of anything else.  Any advice you could give me would be appreciated.

Answer
It is possible someone replaced the sending unit for the gas gauge and in doing so, open the access plate on the top of the tank. The gasket on these is very hard to get in place properly without a lot of care.

I would get several people to help me and position them arround the car to 'sniff' them I would gently blow into the gas filler tube (can be done with just your mouth and a rag. Have them listen and smell and see if the leak is coming from top of tank, engine compartment, or a liquid leak.

Usually just vapor leaks are blown away when driving. A persistent odor is usually a sign of liquid.