Two guys named Fastner and Larson back in the 1979-1981 period did a lot of portfolios for SQ Productions (Sal Quartuccio, out of New Jersey).
They are probably most famous for their Spiderman Portfolio, Hulk Portfolio and X-Men Portfolio releases in that period. Which were advertised in all the Marvel magazines and fan publications of the time
Here's a link to their site, with images and blog entries going back to early 2004:
http://www.fastnerandlarson.com/fandl_images/hotstufcvr_sm.jpgWith many images going back all the way to their first work (that I'm aware of) doing a cover for SQ's underground anthology
HOT STUF' issue 6 (Winter 1977).