Yeah 03+ everything runs through the BCM. You may have to get it reprogrammed for the power seats.
For example, if I wanted to add power everything to my truck, I'd need a new dash harness and a new BCM that's programmed for power options because I have none.
I'm using the BCM and entire dash harness that runs to the fuse block under the hood from a Z71 Suburban, so the BCM shouldn't need to be reflashed.
Maybe I'm just a dumbass and a fuse is blown.