CS,
Well the a/c weren't modified aerodynamically in any way. It's my recollection that all civil TriStars had the vortex generators.
There were two lots of a/c though...ex BA and ex PanAm. There were significant differences in that obviously they were certified by different agencies. The PanAm a/c had digital AFCS when they arrived no RSB, and different schedules for the MDLC. FAA had not found it necessary to fit this spec as did the Brits.
It is probable therefore that the photo youv'e posted is of an ex BA, since these were the only ones converted to tankers and that the the votex generators were only fitted to the BA a/c....memory is a bit hazy on this so will have to check.
Incidentally even the ex BA a/c had structural differences. The first two came from Lockheed with weaker outer wings since they were originally built on the line with 'normal' -200 wings and only during flight test were they stretched. All later production a/c had 'stronger' outer wing sections and thus had a different MDLC schedule!