Is there a filter in the gas tank of 1978 Chevy G20 van?
No, a 1978 Chevy G20 van does not have a fuel filter *in* the gas tank. The fuel filter is typically located in the fuel line, usually somewhere between the fuel tank and the carburetor (or fuel injection system, depending on the engine). You'll need to consult your owner's manual or a repair manual to find its exact location.