Part numbers often change during a models lifetime even for the same part. I had the same issue when I needed a crash sensor for my e38. I think there were four different part numbers which were all compatible in the end and I think I even ended up with one from a Z3/4 I cant remember.
If you go to realoem.com you can do a part number search and see if its compatible with your car. Also if you start with your chassis number you should be able to find the part from the diagrams and it should say in the lower part whether the existing part number has been replaced or not. You can do the same thing on the Pelican website, I think they also allow you to work out the 'flow' of the part numbers from the first to the last.