Did GM change the design of the waterneck gasket at some point? My FSM shows it to be a flat gasket that covers the are extending around the 2 bolts. Alldata shows the same. Autozone only carries an O-ring for the water neck, and thats what my local stealership has listed. Is the O-ring sufficient? I bought a delco thermostat to install when I replace my pump and it didn't come with anything as far as seals go.