I've got another request for info. Can anyone help Barbara?

My father was a retired GYSGT, he passed away in 2000. His name is James Howard Dodd Jr..
I would like very much to find out which "unit", if that is what it is called, he served with in Vietnam. The earliest I know that he was there was 1962, the year I was born. I know from letters to his father and newspaper articles that he was in South Vietnam. Some letters mention him being a gunner.
Can you tell me how I can find the info I am looking for?

I thank you for your time!
Barbara Dodd LaForge
Riverside, CA

usplusfour@charter.net