First, I want to send my condolences ( although very late)for the loss of your son. Having children of my own I can imagine how hard it has been for you over these years losing your son.
We were all brothers who shared a significant portion of our lives with each other.I was at Two Bits when your son was there, however, the batteries had their own locations on the LZ.We did talk to each other on the flight line and I may have even talked to your son, but to be honest I do not remember. We all were fully aware of the loss of one of our own irregardless of which battery he served in.I am sure at the time we all mourned him and felt our deepest sympathies for his family.I and my family hold my fallen brothers in deepest regards for their sacrifice, they are never forgotten in my thoughts and prays.
Yes, it is difficult to find personel from the 2/20th, especially from the early years (65-67).There is a site which you may have already found www.bluemax-ara-assoc.com, which deals with the 2/20th.Although, they do not have a lot of information on those early years.When I contacted them they did not even have me listed as serving with them. They do seem to have a better listing of those who gave all, you may be able to contact someone through them that knew your son. I wish you the best on your search, God Bless.