Both P1 and P2 seatbelt mechanisms are interchangeable. I tested a P1 seatbelt mechanism on a P2 and vice versa and everything seemed to be working fine. No SRS light came on.
The only one thing that looked different was .......................... the colour of this small part. See the photo below
Above the green highlighted oval, you can see a blue plastic part. On the Phase 2 cars it is blue and on the Phase 1 cars it is black. As I said before both P1 and P2 seatbels are interchangeable.
The only thing to look out for is the buckle. On the late 2003-2004 model, the buckle on them has 2 smaller rectanguler holes instead of the 1 larger rectangular one on the earlier models. Hope this helps
See photos below:
