The Dash-80 really wasn't a prototype. It was a technology demonstrator. The fuselage was derived from the Boeing 367 Stratocruiser. I'm not quite sure if the wings were adapted from the B-47. The fuselage width of the KC-135 wasn't settled till the first order for them came from the USAF. Boeing later was forced to make the commercial 707 fuselage four inches wider after Pan Am ordered 25 DC-8's be delivered after the first 20 707's.
It looks like its been made with bondo!
I used to have to walk beneath the wing of a parked 720B (which is still flying for Honeywell as an engine test bed) to get to the crew bus, it was a well worn PA bird. Rivet city, not pretty up close!