It's been awhile since I was in the C-5 program, but my recollection is that the engine was a 58,000-60,000 pound thrust flat rates to 50,000. The reason for the flat rating was to maintain a relatively low Vmcg and 50,000 pounds was sufficient to meet the required take and cruise performance. One parameter, OBE'd, was gross weight take-off at LETO at 35c. Increased climb made much of the fuel savings.
GF