My query was based on something read years ago and, the vagaries of memory being what they are, I am likely guilty of having conflated something someone said about Sartre as opposed to remembering something articulated by Sartre himself. Given that, it's probably not a surprise that no one has found a smoking gun, an article where Sartre describes his life's typology. Moreover and to Sand1's excellent point, my use of the words complete overhaul of the foundations of his thought from the group up almost certainly overstated the case.
As the Playboy interviewer (linked by Gordon) lurches from question to question, there is a suggestive moment where Sartre says, "'Original choice' is the term I use to describe what happens at the moment — a protracted moment, covering a certain span of time — in which one makes something of oneself, of that self which so far has been made by others. We start by being made by others, and then we remake ourselves, starting out from what others have made of us. But at the moment when we remake ourselves, a dialectic comes into play: We find ourselves very different from what we expected and what others expected of us.”
Extrapolating from that comment, from the interesting comments and answers posted to this thread, the excellent links to both the Playboy and NYRB interviews as well as a wiki article (https://en.wikipedia.org/wiki/Jean-Paul_Sartre), one can glean a proto-typology which form reasonably unambiguous periods in his life, thought and work...experiences and moments in his life which were transformative and in all likelihood resulted in such a remake. But is that 2, 3, 4 or more periods?
Fabricating a very rough chronology then, there are Sartre's earliest, self-described aspirations to be a novelist and professor of literature. In the 20s he read Henri Bergman, met Raymond Aron, attended lectures by the neo-Hegelian Alexandre Kojeve, etc. -- all of which were drivers of his evolution into becoming a phenomenologist philosopher. At the end of that decade he met Simone de Beauvoir, his intellectual equal, a woman who became his lover as well as a profound influence on his life. Throughout the 30s he taught at various lycees and published several books. These pre-WWII decades appear to be ones with a slow evolutionary drift from phenomenology into existentialism and Marxism since (as Sand1 notes) by 1943 he had published Being and Nothingness -- a foundational existential tract.
Sartre describes WWII as having had a profound transformative influence on him: as a French soldier, a German POW and, after his release, an activist partisan living in Paris experiencing revulsion at being asked street directions by the always polite occupation soldiers.
His post-WWII life was one of intellectual activism as an existentialist, Marxist and contrarian -- the years in which he wrote his greatest works.
Finally, only the wiki article describes him in his last years as a disillusioned anarchist.
Given all of that it seems to me that one can make the claim that Sartre's philosoph(ies) evolved significantly over the course of his life. Choosing to regard Sartre's life from childhood through to 1939 as a single period in which he wrote and taught is one possible partition. WWII and the publication of Being and Nothingness constituted a radical rupture from what came before and was, perhaps, another period. The post-war years of intellectual activism could constitute yet another period. But where is the moment, the inflection point, the span of time which partitions his life into the disillusioned anarchist of his last years?
Typologizing may be an inherently human trait but typologizing anything is always problematic, reductionistic and fraught with heterogeneity, i.e., less than pure groupings. Ironically, critiques of periodizations are the stuff on which academic careers can be built. Regardless, typologies are useful heuristics insofar as they lend explanatory structure to otherwise formless streams of human experience, space and time.
Sartre was an important figure and thinker in the 20th c. In his case some periodization of his life is both helpful and insightful. Thanks to all for these useful suggestions.