cabin
You are correct. The basic configuration of the 707 was not changed but the fuselage dia. was refined and adjusted to meet customer requirements. The 707,720,727, and 737 all had the same upper fuselage dia. but the 727 and 737 had a shallower lower lobe. The KC-135 had a smaller upper fuselage dia. than the commercial 707 but the VC-137 was the same.