I am with you there, my 70 S was mouse filled as well, can hardly wait to replace the headliner. I love that you are going Olds powered with this car. I thought only myself was the one tearing out sbc's and replacing them with Olds V8's. I would use high temp RTV and double up the gaskets for the headers, it has worked for me. Let it set up for a while so not it isn't as messy. Don't over look the Dodge Stratus fans, they fit the G body rad like a glove and move serious air. My suggestion is have a manual over ride on your fan controller, I have had so many controllers, thermal switches and relays fail.