you project is not supposed to be too overlapping with any case study or the examinable content of any other hsc or sc course, so just double check, cos theres a large portion in the JFK case study about indochina -- that might be a starting point for you particularly the historians Sorensen and Schlesinger.
(Schlesinger i think was a historian in the time of Eisenhower too, and thats when the US STARTED its intervention in Vietnam. -- but of course you knew this)
Anyone that wrote anything on Lyndon Johnson will be good re: Vietnam.
good luck and have fun!!