Edelbrock Intake Issue

If using the old style (large) thermostat housing NAPA sells cast iron housings (maybe from Dorman?). I think they are less prone to warping. You might google Real Gaskets, an outfit in Tennessee that makes silicone gaskets. I haven't had much luck with some of ther stuff (valve cover gaskets), but their thermostat gasket is great - if you try them FOLLOW THE INSTRUCTIONS.