Cover image from Amazon.com sometime.
That front cover gives illustrator, price, and catalog ID.
As of 2018-12-08, Amazon.com provides front cover image of a later edition/printing --identified as such by price $1.95, catalog ID 77040-- as "Avon Books; 1st edition (September 1, 1978)" and this ISBN (which fits ID 40311).
Cover artist is presumed to be interior illustrator Wilson, as for all four Matthew Looney books.
