I can't speak to the T5 checklist, but Old Cardboard's website has the most complete gallery of W600s that I am aware of. There is no Sullivan shown in their gallery. W600s were issued as premiums and were only distributed as they were requested. So, many players may have been available (according to ads in the Sporting News publication), but if none were requested for a particular player, none would have been issued. That said, the "checklist" for the W600 set is very likely too be impossible due to this. Others here collect the set and may be able to speak more directly to whether a copy of Sullivan was ever released and survived, but it isn't surprising that a copy would be extremely difficult or impossible to find. It is due to their distribution method that more popular players survived in greater numbers.
Good luck!
http://www.oldcardboard.com/w/w600/w600gal2.asp