What are the major differences between A904 and A727?

thanks guys this is great information. even if the 727 book doesn't provide me with parts interchangeability at the very least it can give me a good brush up on automatic transmission and general performance upgrades. i am a new truck and transport journeyman but don't deal with automatic transmission. the closest thing i come to is an automated manual transmission. i have torn down and put back together a couple allison transmission while in school which makes me believe i am more than capable of doing my own 904. however i am the furthest thing for an expert. thank for the info guys