Not exactly sure what you mean by the inside of Back to the Future. If you mean parts of the building that were left untouched when the Simpsons moved in, I have heard that in the child swap room on the bottom floor of the attraction, there is still an attraction warning sign detailing that it's a time travel chase. If you mean props from the ride, I can confirm that pretty much all of the props were saved and are currently in storage at Universal's warehouses, though sometimes they are re-used for HHN.