Occasionally I will poke through the net and perform various searches to see what else is out there. Yesterday I did a "540th" search on Google and will list some of the sites I found.
Operation Dragoon order of battle
Scroll down to see Henry Grisell (36th) on her page
The 85th Engineers - Landing in France - I already have his link on my main site...
Veteran's Day '44 - What were WWII vets doing 70 years ago today? - One of the veterans listed was a member of the 540th
Arthur Giggee, who repaired motor vehicles, was with the 540th Engineer Combat Group, U.S. 7th Army as it advanced through the Rhone River Valley as a part of the southern invasion of France. In November, he was in the Alsace Lorraine area of France, although he had already been in North Africa, Sicily and Anzio.
Go2War2NL - Shows how the 540th was in support of the 82nd Airborne - Sept '43
United States Army War College in Carlisle PA - They have documents in their archives. I really need to go there. Maybe this fall when I am in PA. That would be worthwhile.