The 03 and up trannies have a 1" NPT fitting for the PRNDL indicator. THe 02 and down have a 3/4" NPT for the park/neutral switch. Also the gear selector arm is different, and the VB electronics need to be changed out.
These are all items that can be fixed with some work. I made a bushing for a 03+ to be used in the older truck. 1"NPT to 3/4"NPT.
I think they are NPT now that we talk about it I forget.