impedence

As I am a person who prefer to keep his equipment "stock", I don't really know what to do here I have a 1981 JCM 800 2003 (100 watts) head and I just acquired a Marshall 1960ax cab (100 watts, 4(x) 25 watts Greenbacks) which has a delightful sound. My JCM 800 is the CSA version (Silver...