The MLX cards actually have twice the number of stations, considering the adjunct extensions. If you simply add them to the end of your cards, you won't have any problems. If you want to change an 008 ATL with a 408 MLX, the station programming will shift. The programming for the 2nd ATL set will move onto the 1st adjunct. The 3rd ATL will move onto the 2nd MLX, and so on all down the line for the rest of the system. It would probably be easier to simply default the system and reprogram if it involves a lot of stations.