* Actually it's the only XB-70 in existence.
Edit: https://en.wikipedia.org/wiki/North_American_XB-70_Valkyrie
The planes are fantastic but the highlight for us was talking to a former F-4 pilot about techniques for dodging SA-2s. Highly recommended.
Tacit Blue is also worth a look. It's honestly hard to imagine anything so ungainly actually taking to the air.
ETA: Dunno if they still have it on display, but for a long time they had just the forward fuselage of Bock's Car sitting unloved in a corner. It's hard to reconcile the destruction unleashed by that single plane with the utter impotence of a piece of it sitting helplessly in a museum.
As to the Bockscar, they have it on display with its payload bay open along with replicas of Fat Man and Little Boy under its wings.
All that being said, the highlight for us was seeing the WWII planes fly overhead and then seeing one of the VC-25As flying past seconds later. Multiple times. The rumor was they were doing takeoff/landing training.
They have a massive range of the history of aviation with a good mixture of foreign birds as well as US aircraft. I'm personally a fan of those classic Douglas planes, they're so incredibly iconic and have quite a showing at the museum.
EDIT: I guess I should clarify the relation to this article. The actual prototype is housed at the Air Force Museum in Dayton, OH along with the C-97 that carried it on display. They have a small exhibit with some example photos of its technology. Its literally right next to the B2 on display.