Neat stuff, Cub. I especially like the last photo of the 407 with the three open hangar doors behind it.That's the experimental department at the Military-Twin Division. I used to sit in the grass with my lunch bucket against the building around the corner from the doors. Of course this was after the 407 project was terminated. The fuselage was still sitting in the fenced in bone yard on the north side of the hangar.
Many years later, when I was killing time at the then new Citation Service Center (the hexagonal one) I walked across the ramp to Experimental to visit with my old supervisor and noticed the center engine and top of the T-tail of the mock up of a tri-motored jet that was curtained off in the corner.
I'm surprised you haven't run across some of the early Citation mock up photos or drawings with the sharply pointed nose and horizontal stab mounted mid fin?