Lego Fire Museum: Yup! It was a nice ol' Crown pumper. Later on in the season LAFD donated the Ward to Emergency!. I heard they used a real firefighter to drive it because they didn't want an actor to crash it.
The first Engine 51 was a Crown Firecoach. It was replaced by a Ward LaFrance Ambassador. The Ward was driven from Elmira Heights, NY, to LA by Mike Stoker who was a real LA County firefighter as well as the driver/engineer on the show.