The max rated N1 is a function of altitude, Mach, and temperature (corner point and the square root Theta term), and of course the engine rating. Boeing has five CF6-80C2 ratings on the 767 - B2, B4, B6, B7, and B8 - and two on the 747-400 - B1 and B5. With the exception of the B8, the engine build is the same regardless of rating. Then just to make things more complicated you have FADEC and PMC (not all those ratings are available on the PMC).
Redline N1/N2 is fixed and never changes, however there can occasionally be some subtle changes in rotor speed redline values between different engine ratings.