Maximum range cruise (MRC) by definition is the speed that will provide the furthest distance traveled for a given amount of fuel burned or the minimum fuel burned for a given cruise distance. For Boeing aircraft, this is achieved at Cost Index = 0, which corresponds to the top of the curve on the fuel milage charts (NAM/lb vs Mach).

MRC is L/D max in cruise, while best hold speed represents best endurance. As someone mentioned, Aerodynamics for Naval Aviators is an excellent reference, and it states that typically best endurance is 25% less than best range. For the 747-400, max endurance is much closer to max range. For example, at 680000 lb., MRC (L/D) Mach is .838 at FL350, or 288 KIAS. Best hold speed for this weight and altitude is 276 KIAS.

For EO cruise, FMCs typically target LRC speed (1% increase from MRC). However, there is an option to select E/O SPD, which again is MRC or L/D max if terrain is a factor for the drift down. This gives the shallowest angle (or longest distance) to EO altitude.

This is repeated for descents at Cost Index 0, which is L/D max to again maximize distance traveled, which means thrust retarded to idle at cruise altitude earlier to minimize fuel burn.