Just looked at the beginning of this thread again and realized that I saw that SP the last time I was at McCarran. I thought it was odd to see an SP, as I knew that only a few were built and they were pretty old. Nevertheless, seeing a short-body 747 sure gets your attention.
I hope the donation goes through and that the museum is able to accept and care for the airplane. About 25 years ago, Northwest donated a 747 to Western Michigan University's aviation department. The department didn't think to look a gift horse in the mouth. Big mistake. Airplane is flown in and parked. Big celebration. Northwest then removes the engines and anything of value from the aircraft. The school has to build a structure to keep the airplane from sitting on its tail. And then to secure it because it's now so light that it moves around in a stiff breeze. They thought that it could become classroom space. I seem to recall that it was going to be too expensive to do that. I think they finally gave up and sold it for salvage.