Can't really tell from what appear to be date codes, except a 1973 casting probably wouldn't be for a Boss. Too much is missing. 2V or 4V size ports, open chamber or closed. Milled rocker stands or standard. Valve size, since '73 Cobra Jet used 2V sized valves.
Those are date codes and useless, other than telling you he most likely has a mismatched set of heads, as one is a 1970 casting, the other a 73. Casting #'s are on top of the runners in the rocker area of the heads. See pic below. Crummy casting # guide below as well.