Andy E. Nystrom wrote:

Hembeck 1980, as reprinted in The Nearly Complete Essential Hembeck Archives Omnibus. Apologies for how crooked it is. Hard to scan a book this size on a standard printer/copier/scanner and it took three tries to even get it looking this good. But I think you'll agree this is a good challenge for trying to ID everyone.

Excellent challenge - and not to lessen your much appreciated effort in scanning the image (if you'd not gone to that effort, I'd not have known the image existed or where to look), here's one scanned from the original title, which meant it could be laid flat more easily:

One of my favourite "modern era" handbook covers:

Cover art for Amalgam Age of Comics - this is the original, without lettering blocking anything but sadly uncoloured.