Looks like Gray's work....that signature could be a"GM," they're boh characters Gray worked on (although Supergirl not 'til later) and Phil Seuling who printed this also did Gray's DARK DOMAIN, Still...not sure.
Alan Kupperberg, artist and friend of Gray Morrow, has gone on to a successful artistic career at Marvel, DC and NATIONAL LAMPOON (amongst many other venues) and now he's available for personal private commissions! For more details you can contact Alan directly at:
First published in 1968 (I was 9!), I have been writing professionally part-time for more than two decades. I have been freelancing for various authors, editors and publishers for the past three years on the behind-the-scenes tasks of writing.