I know a guy who was there, who says it was the other way around. He was with the 42nd, says they liberated Dachau proper and the 45th liberated a subcamp.
On 29 April 1945 Dachau was surrendered to Brig. Gen. Henning Linden of the 42nd Infantry Division of the U.S. Army by Untersturmführer Wicker.