I have a 1967 camaro with a small block without a/c. My interchange manual states that the core is 2 1/2 inches wide. When I ordered a heater core from a local part store the core is only 2 inches wide. Will this be a problem? Should I keep looking for the right thickness? Will the 2 inch wide heater core work just fine? Where can I get a quality 2 1/2 inch wide heater core? Please help me!!!