A couple of links I found while searching for other stuff. Posted here for posterity (so I can find them again later) and just in case someone here can use the information. Full disclosure: I have no connection to these sites.
AMC 258 block, head and crank casting number key.
A slew of links to Jeep technical info on engine, emissions, carb and CARB. Some diagrams, etc.
AMC 258 rebuilding tips.