There are two places on the web you can get this information. The first is http://neds.nebt.daps.mil/o1650.htm. This isn't too good except for one thing. Under the list of awards and abbreviations there is an OPNAV 1650 note indicating that both the Gallantry Cross and Civic Action unit citations were awarded to MACV and all subordinate units (which means all military personnel in country) between the early 60's through 28 March 1973 (you should be eligible for both of these). The down side is the Marine Corps unit citations listed are from the late 80's through the 90's.
The best place to find other unit citations (PUC, NUC, MUC, etc.), by unit and eligibility dates, from WWII to the present follows: (P.S. you need an acrobat reader to open this 256 page Marine Corps awards manual) if you do not have an acrobat reader just do a web search for acrobat reader and you will find many sites you can obtain if from (it's a free download).
Go to http://www.usmc.mil. Check publications, check orders/directives, check navmcs, check on NAVMC 2922 (Unit awards manual), then download the acrobat file (remember you will need an acrobat reader, preferably 5.0) Like I said this is a 256 page document and will take a while to download; but, with the possible exception of Iraq, it has everything you are looking for except the Gallantry Cross and Civic Ation unit citations because these were issued by a foreign government. Hope this helps. I found three I was eligible for. Your local Veterans Affairs representative; or, your regional VA office can provide you with the form you will need if you wish to have these citations ammended to your DD214 (with a DD215). Doc.