I can only suggest you use an on line parts catalogue and research each item. For example SNG Barretts illustrated catalogue gives part numbers and in most cases the applicable chassis numbers. Using front seats as an example, four types are listed for the series 1 and by examination of the relevant chassis numbers from type 2 onwards you could work out which ones are original for the car you are looking at. It will be time consuming. Good luck!
Robbie
Robbie