Per the all-knowing Wikipedia, there are conflicting conclusions between the GAO and the DSB regarding the cost-effectiveness of switching:
"For a study for the U.S. Air Force in the mid-1970s, Boeing investigated replacing the engines, changing to a new wing, and other improvements to upgrade B-52G/H aircraft as an alternative to the B-1A, then in development.[104] Boeing later suggested re-engining the B-52H fleet with the Rolls-Royce RB211 535E-4.[105] This would involve replacing the eight Pratt & Whitney TF33s (total thrust 8 × 17,000 lb) with four RB211s (total thrust 4 × 37,400 lb)—which would increase range and reduce fuel consumption, at a cost of approximately US$2.56 billion for the whole fleet (71 aircraft at $36 million each). A Government Accountability Office study concluded that Boeing's estimated savings of US$4.7 billion would not be realized and that it would cost US$1.3 billion over keeping the existing engines, citing significant up-front procurement and re-tooling expenditure, as well as the RB211's higher maintenance cost. The GAO report was subsequently disputed in a Defense Sciences Board report in 2003; the Air Force was urged to re-engine the aircraft without delay.[106] Further, the DSB report stated the program would have significant savings, reduce greenhouse gas emissions, and increase aircraft range and endurance, in line with the conclusions of a separate Congress-funded study conducted in 2003.[107] In 2014, the U.S. Air Force was reviewing industry studies of engine replacement.[108] The re-engining has not been approved as of 2014. In late 2014, it was reported that the DOD and unnamed private companies were exploring a leasing program where private lease companies would purchase new engines and lease them to the USAF. DOD costs would be determined by depreciation and actual usage with no up-front lump payments.[109]"
. I was thinking more in the line of sticking some type of Williams or other compact efficient design in instead.
