There was a special mod of the KC-135 designated KC-135Q for the refueling of SR-71 and U-2/TR-1 aircraft. Apparently the tanks for the JP-7 were isolated from the ones that fueled the tanker with JP-4.
Didn’t also the KC-135Q have modified engines to fly faster and basically they would fly as fast as they could and the SR-71 would slow down as slow as she could.