Pretty much everything
The only different bits between them that come to mind are the camshafts inside the engine , front brake discs and calipers , and the ecu which will be programmed differently.
Particularly useful to store are the inlet manifold and VIS motors , oil cooler , assorted water pipes and door mirrors . If you have room , I would have front wings and both bumpers in case of accident damage , and if he doesn't need to move it then I would have the rear suspension arms which are known to rust ! Oh , and the exhaust system complete ...... in fact , just take the car off him
