If the 04 doesnt have an internal SCM allready than it shouldnt be working at all.
akaowners.org will give you good results. Most of the guys there will have at LEAST an internal SCM you can practically have for free, and likely will have an SCM 2 you can buy. I never really heard the bad things about the 3 though.
When you send your gun to DC - i suggest getting there NOT FSP milling, and then having them mill out the pocket behind the ASA. It looks alot cleaner and its just super cool..and its what i want to have done
Do you know if your 03 has humphrey solenoids?