Yeah, "stewed dog" not only rhymes, but also conveys some of the quahog "ambience." So would "rotten log."

I'd be tempted to use the word in the middle of a line (where a rhyme might not be necessary) or, if I put it at the end of a line, end the couplet with something that rhymed with "clam" instead--and grin when I sang it.

Joe