The Grand Forks Air Force Base flies the KC-135R. They were very proud of the R-upgrade.
Photo by Bob Nelson at the GFAFB 'Friends And Neighbors Day' on May 27th 1989.
The second modification program retrofitted 500 aircraft with new CFM International CFM56 (military designation: F108) high-bypass turbofan engines produced by General Electric and Snecma. The CFM-56 engines are capable of producing approximately 22,500 lbf of thrust, nearly a 100% increase in thrust compared to the original J-57 engines. The modified tanker, the KC-135R, can offload up to 50% more fuel (on a long duration sortie), is 25% more fuel efficient, costs 25% less to operate than. It is also significantly quieter than the KC-135A, with noise levels at takeoff reduced from 126 to 99 decibels. (Wikipedia)