Israel's tankers are conversions of the 707, which due to its 4-inch-wider cabin, is differentiated from the -135 family by Boeing (indeed, Boeing briefly used the 717 designation before adopting the USAF designation of C/KC-135). The only countries to actually buy -135s off the line are the US and France (-F models); the US later sold some surplus aircraft to Turkey and Singapore.
Also, 707s that were used for transport by the USAF/USN (as opposed to radar and C3 duty) were termed C-137s (the most famous of which were the former Air Force Ones).
I wonder ? if they can build new tankers from the new BOEING 747 ADVANCED ( but still will be the 747 - 500 series in my book, this is ? if they even go ahead with making a new version of the 747 ) if they can get the operational cost down of operating the 747 , could it make a nice sized tanker for the US military ?