Valve Springs
Just a FYI. I don't know what year, if at all, it changed, but. Back in the 1960's and 70's the slant spring and the 318 spring were different as installed new from the factory. If you ordered "replacement" slant six springs from the dealer you got the 318 springs. Unless you are having a problem caused by your stock springs, changing the springs will not make any performance improvement.