My pal reports back:
"I referenced the address printed in the Natural Disasters comic with the publisher addresses listed in the 1954 Senate hearing transcripts and GIS has the same address as Toby Press."
So 'Graphic Information Services' is an imprint of Toby. I don't think the publisher, Elliott Caplin, getting his brother, Al Capp, to lend his authority by having one of his studio guys draw the cover, needs too much explanation.
Now, The MLK book has 'published by the Fellowship of Reconciliation' on its final page. Since the Fellowship was not in the business of publishing comic books we may presume that a regular comic outfit packaged it for them. I note that the natural Disasters book is copyright 1956, which is after Toby closed its doors. If Toby was trying to continue in business as GIS, we might presume further and say that The MLK book was packaged by them. (with Toby down, one could imagine Al Capp providing that cover to help his brother stay afloat, since L'il Abner isn't really connected to the subject in any way). Perhaps Al lent his name to one or two other things, which is where the Capp-Toby confusion originated. perhaps his name was on 'the board of directors' or whatever.
We went on a diversion there for a while, which did end up proving that Toby went into the business of publishing public information pamphlets in comics form, something we didn't know when we started. So that leaves us with two books published by Graphics Information Services, and now two unidentified artists. Still, we've come a long way on this inquiry. I'm sure if we had more of those Toby romances to look at we could find our artists (The romances use more prosaic real-life drawing than the adventure and horror, whic is what we need for comparison here)