Re: Why the 1970's?
I also just checked what was going on in 1973 as far as Vietnam. Here is what I found:
"The Paris Peace Accords of 1973, intended to establish peace in Vietnam and an end to the Vietnam War, ended direct U.S. military involvement and temporarily stopped the fighting between north and south. The governments of the Democratic Republic of Vietnam (North Vietnam), the Republic of Vietnam (South Vietnam), and the United States, as well as the Provisional Revolutionary Government (PRG) that represented indigenous South Vietnamese revolutionaries signed the Agreement on Ending the War and Restoring Peace in Vietnam on January 27, 1973."
This seems like a perfect polt point for the movie!