https://taint-the-meat.com/2013/08/04/x-men-portfolio/#more-1715

A cool project from 1980, Byrne worked on 2 of the 4 pages for the X-MEN PORTFOLIO, published by SQ Productions in 1980. What appears to be Byrne pencils or layouts, airbrushed and painted by Fastner or Larson.

Without Byrne, Fastner/Larson also did a HULK PORTFOLIO and a SPIDER-MAN PORTFOLIO, all in that 1979-1981 period.
And a later 2nd X-MEN PORTFOLIO, without Byrne, and I think less impressive without him.

From that period I described in my opening post, a time where Byrne pretty much strode over the industry like a god.