At risk of hijacking this thread AND sounding like a complete anorak.......
We parked up near this aircraft recently and I noticed the engines (or maybe just the cowlings) are very different to the usual engine/cowling combinations that you normally see on the venerable old 707.
Here is an old picture of N88ZL with the "normal" engine/cowling combination:-
http://www.jetphotos.net/images/b/B.....jpg.29982.jpg
And here is a close up of the same aircraft taken some years later, after a respray, and with very different looking engines/cowlings;
http://images1.jetphotos.net/images/....jpg.71180.jpg
(Mods. feel free to move my post to any other forum if you think it appropriate. CC)