Top one is a drool tube head in production from '60-'74. The bottom one is a peanut head that was in production from '75 on. It really isn't a bad head since it has hardened valve seats and no spark plug tubes to leak, although it uses 5/8" spark plugs and heat range selection is limited. If there is no AIR injection port beside the rear exhaust port it is a '75 since AIR ports showed up in '76. There is a pad on the block deck near the front passenger side corner with the ID info stamped on it. You usually need to remove the alternator bracket to see it. Those numbers will tell all you need to know about the engine....
