I think the Al Lewis/Blueberry Hill connection is nothing more than another urban legend created on the internet. My guess is someone saw the name Al Lewis and mentioned that the guy on the Munsters was the same guy who co-wrote Blueberry Hill and that assumption just snowballed on the internet. His obituary in the LA Times says nothing about him as a songwriter. The only thing it said was that he initially was listed as being born in 1910 but his son said his real date of birth was April 30, 1923 which would have made him 82 when he died not 95. Even IMDb lists the songwriter Al Lewis as a different Al Lewis....Al Lewis (V).
imdb.com/name/nm0506893/ Here's a link to his full obituary in the LA Times including a "for the record" update about his age.
articles.latimes.com/2006/feb/0...lewis5