Hello fellas, I am new to this forum thing. I have a '65 Riviera & I sent her 401 out to the machine shop for a rebuild. I've owed her for about 20 years & shes been sitting for 13ish years. While the engine is out I was gonna pull the heater core thru the firewall. Thats when I learned it doesnt come out that way unless I cut a 1/4 inch around the opening. My question: if I cut it out will the core now be floating/rattling around in the heater box without the metal that I cut to hold it in???