If I was actually going to put a pinball in a time capsule, I'd go with something

1) Unlicensed. When they open the capsule a thousand years from now, they're not going to know who Metallica are.

2) Probably EM, so that the people of the future could fabricate replacement parts more easily. If there's a solid state machine with completely open-source components, I might go with that.

If this was for a museum, and not a time capsule, I'd probably skip the EM requirement and go with MM or Getaway.

In either case I would include as complete as possible plans, part-lists, repair guides, for the machine as a whole and also each individual components. On paper, on microfilm, and (if it's going in a time capsule) also etched into a piece of aluminum. (Probably on a digital format too, just for the hell of it, though I wouldn't expect it to be useful for too long.)