not really a way to identify it unless you drop the tank. If you disconnect the fractory fuel line and run a 3/8 rubber hose from it into a can, and then put 12v to the fuel pump test lead you can determine IF it is a stocker or not. A stock fuel pump in good health with a clean screen and clean filter will free flow nearly 1/2 gallon in 1 minute. A Walbro GSS340M pump will free flow a bit over 1 gallon in a minute with all the same circumstances. If you drop the tank, the pumps are cheap enough to just replace it any way.