Strange, I have never seen a air cleaner option on a fender tag. I can't find a E1 option in the books except for a 6.50x13 tire option. Interesting stuff.
Mike, flip back to page 2 of this thread and there's one of the tags with the E1 code on it. It stands for sales code 471, mandatory in California. Just looked at this guy's punch card, and it also has sales code 471.