"Not sure where you "heard" this story, but, if true, is just an interesting bit of trivia. Has absolutely NOTHING to do with safety, airworthiness or operations of the E-3Ds".
But it did! Not being a spotter, I do not know which "707 type" wings fit which....however in the Sentry case, the internal structure of a replacement wing from a different (if similar type) of aircraft was different to that in the design drawing and this caused EMI problems in the mission kit!!!! (lack of suitable shielded cable runs). This is exactly what my point is - even small changes can have knock-on effects. While not affecting the safety of the individual aircraft, a loss of performance in the mission system of the Sentry could have affected the safety of our "customers". It is this point which also has implications for RoS of an ISTAR aircraft. If the mission system gets things wrong then people off the aircraft can be affected or even killed (eg if the system mis-ids an object due to technical issues or misses a threat warning). Therefore, in this case, a Sentry was not the same Sentry as the rest of the fleet until it was modified to cure the problem.
Never assume, Check!!!