Boeing C-135FR Stratotanker (59-1450)

KC-135R Stratotanker

Based off the Boeing 707 commercial aircraft design. Over the years the military KC-135 has been consistently upgraded and improved......new wings, avionics and engines.
The old original Pratt&Whitney engines have been replaced with the new CFM power plants which are quieter, more fuel efficient and provide greater range.
When the KC-135s were re-engined, they were then designated the KC-135R.

Jim, the KC135 is actually based on the shorter fuselage B720, still highly modified and strengthened compared to the base model.