I have no evidence whatsoever that they were used in the D-Day landings, however,
the British
and Americans used them in Europe!
Most of the deliveries were to British units, while some were assigned to the 79th Armored Div., the same div. that used the funnies, DD Shermans and the like. Some of these were modified with anti tank guns, a few were fitted to lay mats over muddy terrain, and some were even fitted with flamethrowers. These were equipted under the designation "Sea Serpent". They were used primarily for river crossings - Rhine and Po rivers in early 1945. They were also used to help secure the approaches to Antwerp in late 1944 against the German held islands in the Scheldt Estwary.
Here's some pics I dug up:
U.S. Army northern Europe 44-45 (LVT4)

British in England with a 6lber rigged.(LVT4)

U.S. rigging a 105mm (LVT4)

One being loaded onto a DW in Holland to cross the Maas River (LVT2)

9th Army preparing to board for the Roer River (LVT2 & 4s)

88th Infantry loading a 105mm onto an LVT4 for the Po River

I'm in touch with a couple sources for further info on the use of the Amtracs in Europe. I'll post more info as soon as it becomes available. Enjoy.
