2001 silverado with manual seats. Had one black wire and another black w/white strip clipped under my driver seat. Got 2006 powered. No heat or memory. All powered up but now the seat belts don't seem to lock with break. Have one blue wire and another black w/white wire not connected to anything on the powered seat that installed. Does the seatblet locking mechanism need some kind of power to?

 

The seatbelt locking mechanism should be entirely mechanical, and is based on what I would describe as a pendulum type device internal to the seatbelt mechanism, which swings forward when braking. That said, here is what I can find for the SEATBELT wiring diagram for a 2006 Silverado:

https://charm.li/Chevy%20Truck/2006/...%20Schematics/

The other diagrams relating to seats and seatbelts are up there too, for both your 2001, and the 2006 the new seat came from.