Compression Issue (thin head gaskets??)

Look for 302 heads, they have a smaller chamber. You could try 66-67 273 heads too, I believe they're 57ccs from the factory. You won't have to look for shorter pushrods then. Mopar had a gasket set that compressed tp .028, but I think they're hard to come by. The other thing to try is a shim type of gasket. They're steel and Cometic might be able to help you. Try asking for a 273 head gasket for the smaller bore.