It sure is easy to document a 61 SS. I think the first thing is the build date. They where only available very late in the 61 model year. From there on it all about power train, casting dates fuel line size etc. etc, but for me the first thing is the build date. I do not think a 61 SS 409 correct block even exist anymore. Why do you have one or are you thinking of buying one.? Which ever way good luck Morley