Edelbrock Intake Issue

Welcome aboard!

The dual bolt pattern allows the use of either the '77-older large thermostat, or the '78-newer small one (which is the same as a Chevy). Make sure your housing and thermostat match--the large stat will never seal in the small housing. Also, The Mr. Gasket thermostat should be avoided due to known quality issues--they have a high failure rate. Get the Stewart/EMP equivalent (expensive, and worth every penny) and use an OE thermostat housing that matches.