[dave-r]

YEAR ONE have this very well put together set of web pages that show you how to identify a block and de-code the numbers on it.

YEAR ONE Mopar Engine Identification

I have given it a quick look and it seems to be well informed. The only mistake I can see is that they say there were no 440 six-packs after 1971. This is not completely true. There were a few 1972 cars (not Challengers) built with this engine although I admit it was rare. You also have to remember that the 440 six-pack was fitted to cars like the Jensen Interceptor for a few years so you may come accross the odd block or induction set-up which dates after '72 even.