Whatever you put in, you really must keep the original stuff you take out to maintain the cars providence for the future.
Slightly different I know, but every thing that has been 'upgraded' in my Mk2 GTI has been packed away so that at some point it can be put back to the factory spec that matches the build sticker. One of my upgrades was to replace the rear seat for one that if 60/40 split with head rests, also electric windows which necessitated a different center console to accept the switches.