I tried Googling "United Feature comic post" but got tons of unrelated hits. "1970 comic post" yielded nothing worthwhile. Same with "comic strip cartoonist post" or "United Feature Post cartoonist." The issue, of course, is that "post" is also the name of pretty much any article that goes online any more, so there's tons of extra noise to filter.
Eliminating the name entirely, I hoped to find a list of comic strips UFS was running in 1970. "United Feature 1970 comic" came back with a lot, but switching to an image search brought in a few comic strips that seemed like the same style. Popping over to the page hosting those images, I was able to see that they were signed in the same way! I believe I've found my answer.
It was a strip called The Dropouts by Howard Post. Doing another Google search on that specifically turns up Post's Wikipedia entry. The strip itself doesn't have an entry, but Post's bio says that the strip ran for thirteen years beginning in 1968...
The premise of The Dropouts was a variation on the "stranded on a desert island" gag. The two main characters, Alf and Sandy, were indeed castaways, but the island is hardly deserted: One of the strips' running gags was how closely the natives' society resembled Western civilization. Other characters, all natives, included a one-man police force, a doctor and a chef running a cafe with inedible food. There were other Western characters, including a religious zealot, an angry feminist and a disheveled alcoholic, Chugalug.Interestingly, he was more of a comic book artist than a strip artist. He worked for Harvey Comics throughout much of the 1960s, and created Anthro for DC. After The Dropouts ended, he went over to Marvel and drew for their Star line of comics in the 1980s, followed by a stint as editor for Looney Tunes Magazine and Tiny Toons Magazine back at DC.
It doesn't seem like Post or The Dropouts are particularly likely candidates for inclusion in any comic strip histories, and a lengthy biography doesn't seem financially feasible either. So stumbling across the art, and then doing a little digging on my own once again has come up with another fascinating little corner of comicdom that's largely escaped the broader history books.