Hello and welcome!
I don't have much new to offer besides the same recommendation of checking up with the National Archives and the US Navy Naval Historical Center like others have suggested. But once you've found out what LST he served aboard, perhaps you'll be able to find a pic of it in action here:
WW2DB: Photographs
There are currently 38 LST photos at that link, which is a part of my WW2 history website.
Best of luck to you!