I saw the MD-21 in Seattle years ago. That plane was beyond mint and had the most visitor friendly display of any of these planes. I think they also had a sectioned engine with the buick starter cart if I remember right.
The walk in display at the Dulles is incredible looking, but that plane is so roped off, it is more like a model kit than an education tool.
Did anyone study the telemetry logs of the SR-71's record setting flight from coast to coast at the Dulles display? I looked like a weirdo studying those blurry logs for a good long while, but there is some incredible insight on how the plane operated on those logs.