"The Chimes at Midnight", by Geoff Trowbridge, tells of the life that could have been, ie. if Spock had died during his kahs-wan practice run at age seven, and Thelin went on to be Kirk's first officer on the Enterprise. the timeline continues on through the movies years, paralleling the Genesis Project years and beyond.
Below (left), here's how he appears, drawn in the Filmation style, in the Titan ST Magazine, US #12, Jul/Aug 2008, p. 56:
Pocket Books cover art (right) by the talented John Picacio