This was the earlier version of "cruise control", from the later '50s or earlier '60s. GM had something similar, but not "Auto Pilot" in designation. The add-on kit for a '65 Impala, for example, mounted the unit on the core support with a LONG rod that went to the carb linkage (from the front side of things).
In those earlier times, factory "cruise control" was not a very high-installation option. Too many "two lane blacktop" roads, back then. Probably great installation rates in NV and KS? When the newer, more compact cruises came online in about '65, and especially the "memory cruise" from Ford and Chry in '68, THEN cruise control installation rates increased, by observation.