Good Morning, Manfred,
I must have overlooked your question when you first posed it. Since no one has jumped in with a reply, here goes:
The Roden E-3A kit has a different set of nacelles than the 707 kit to reflect the appearances on the real aircraft. The Pratt &Whitney TF-33A flown on the E-3s is, at its core, a JT3D just like the airlines used. But the engines hanging from the E-3s look “beefier” than their civilian cousins. I suspect that the core accessories laid out around the engine turbine are more robust — bigger generators to produce all the power needed to run the myriad electronic systems on the E-3 — and therefore require a larger space and a different shape.
Here is a shot of the sprue layout and a drawing of the two versions of decals found on Roden’s website (http://www.roden.eu/HTML/345.html):


I hope this helps!
Cheers!
Tom
Edit your Profile to get a forum signature.