Thanks for the reply. I agree, just providing a positive & earth for the seat electrics is no problem, but I just thought that whilst there was no interior in either car I could remove the airbag ECU and cabling from the newer car and put it in the older car, complete with passenger airbag etc and therefore have seat airbags as well.
My question was essentially, is this possible or are there any fundamental differences between a CF 2 car and a CF 3 car that would prevent this? Presumably the power to the airbag ECU comes from the same source? Replacing one whole airbag system with another whole system would seem possible, but I am happy to accept that there are reasons why not.