I thought I'd seen this art before!

I looked through AMAZING ADVENTURES 27, Nov 1974, one of the McGregor/Russell Killraven issues.
A version of the above page (cropped and small) appears on page 12 in an ad for Steranko's MEDIASCENE
magazine. The ad probably appears in all the Marvel titles for that month.
So it must have appeared in a MEDIASCENE issue prior to that date.