Interesting. That was before the advent and heyday of the "double wide" mobile home.
Not that a YF12/A12/SR71 would have quite fit but Lockheed soon built a solution to the overland route to Area 51 - the C5A. In about 1983 we'd look across the field (BUR) at night and see a C5A parked next to Lockheed with a white curtain from the building to rear door. It wasn't hard to figure out they didn't want anyone to see whatever it was. It was the F117, going to Groom Lake, AKA area 51. The flight would have taken about 40 minutes, not three days.