Rusty,
AD = Advance-Design (1947 to 1955 first series). There is no "d" on the end of Advance. Art Deco is a common name of the earlier trucks but not an name officially used by GM
The 1946 models were sold into 1947 but were called 1946 by GM.
What differences do you want to know? The seats on A-D trucks are 8" wider and the cab mounts are different.
51 Jimmy would be your best source of first-hand information about how the cab mount differences, and if your older cab will be outside or inside the frame rails.
Here is a GM article about changes in 1947 compared to 1946. Tim
