Not sure if others have seen this, but I found it interesting:
https://groups.yahoo.com/neo/groups/ditkomania/conversations/topics/3314
It also got me looking into the Post-PHM legacy on the GCD:
"I'm struck by the fact that TOS #54 (June 1964) was special for a reason previously unknown to me -- it carried the last Marvel (non-series) fantasy 5-pager of the early 1960s: "Skrang Strikes Tonight!" by Stan Lee, Larry Lieber & Ayers. The final non-series 5-pagers in the other anthologies came earlier: Strange Tales #113 (Oct. 1963; which had two fantasy back-ups including one by Lee & Ditko), Tales to Astonish #54 (April 1964) and Journey into Mystery #104 (May 1964). The end of an era!"
So TOS54 appears to be the end of the line if you extend "PHM" and exclude the Tales of the Watcher/Wasp/Asgard stories.
Sorry if I'm re-hashing something discussed pages ago, lost track of all the rabbit holes this single thread has taken me in this hobby!
-bc