Exactly my point - one of the E-3Ds has the wrong wings on!! It may be that they are 135 type wings and from an E-8 or similar
Where to start, the E-3D is a derivative of the Boeing 707-320B, the KC135 was direct derivative of the 367-80 (some confusion comes from the fact that during the studies carried out in the early 50's Boeing that led to the 367-80 used the 707 designation for the concept models, for instance 707-1 had four engines in two pods similar to the engine mounting scheme used on the B-52, the 367-80 was based on the studies carried out under 707-6, further research made this the 707-7). The wings of a -320B are longer, wider and thicker and have different flying control configurations (Flaps/slats/spoilers etc.) to those fitted to a 135. 135 wings couldn't be fitted by mistake, it would require extensive modification.
The E-8's are all converted 707 airliners, no new builds, so no E-8 wings on an E-3D. One prototype E-8 was an ex E-6, however this was sold to Saudi Arabia as an RE-3B. The E-6's and the E-3F's were on the production line at a similar time to E-3D, perhaps this is where your rumour stems from, however, these again are -320B platforms not 135 platforms.