Great info, HT! I don't think I've heard of those early films.
I remember there being some discussion here or somewhere else about a novel about Vietnam that included references to hairjobs that US soldiers got from local long-haired prostitutes during the war. Can't remember the name of the book, though.
I remember references to long hair in The Joy of Sex, though Alex Comfort never used the term hairjob. Something about making a plait that could be used as a substitute for a vagina.
My biggest influences were the hair fetish letters in Penthouse Forum in 1974-76 with titles like Hair Streaker, Brush Up and Comb Down. Those really got me going on long hair!