So far all FedEx 757 are fiited with the RR E4 according to this site-
The Boeing 757 website - FedEx Also the 2 latest purchases are sitting in EINN awaiting ferrying to ST Aero in MAE they are ex Thomson Airways G-BYAK & G-BYAS, I was talking to one of the aircraft conversion team from MEM who was over doing some prep work on site in the Air Atlanta hangar EINN.