Seeking records of 17th Tank Bn, 273rd, 330th & 414th Infantry Regts

Good Morning!

I have been slowly piecing together my grandfather's WWII military history.  He rarely spoke of his service but had a few documents and about 200+ unlabeled photos that I have been trying to identify.  From what I have pieced together, over the years, he began with the Company H, 330th Infantry Regiment, 83rd Infantry Division, and was transferred out due to an injury in August 1944 (morning report).  I would like to fill in the gaps of where he was transferred past this point.  Through pictures and a GO order of him receiving at Solider's Medal, I know that he transferred at some point to the Company M, 414th Infantry Regiment, 104th Infantry Division.  I believe he was with the 104th at least by November 1944 and was most definitely with them by February 1945 when he received the Solider's Medal. 

He also has photos with the 7th Armored Division and his discharge papers list him with the Headquarters Company, 17th Tank Battalion, 7th Armored Division.  He has a ration card attaching him with the Company C, 273rd Infantry Regiment, 69th Infantry Division in August 1945.  There are pictures on the ship before returning home of soldiers with the 69th ID as well.  I would love to travel to St. Louis to pull morning reports and any other documents that would be helpful to fill in some of the gaps of my grandfather's military history.  I been to the National Archives website and I am aware of what I will need to do in order to register in preparation for my visit.  I have been told that I need to be prepared with box numbers so that they know what to pull.  I am unsure where to even begin to find the box numbers.  Any advice or direction you can provide will be greatly appreciated.

Lastly, in 2014 I began assisting teams in France in the return of WWII military relics to families in the US, free of charge.  We have returned close to 40 at this time and I am researching another 80 items.  I volunteer to research the solider's military and civilian history,  build family trees and locate living descendants or spouses, unfortunately I have not come across a living solider in order to return it directly to them.  I currently use Ancestry, Fold 3, FamilySearch, Newspapers.com and infantry division websites to pull information.  If you have any other suggestions for worthwhile resources that I may have missed I would appreciate advice in this area as well.  It is a way I honor my grandfather's memory and that of these brave solider's.

Thank you so much for your time and assistance!

Elisa Vaught