This change will affect the 90/130,180 and 250 cc variable pumps and motors
They are changing the cylinder block running face, outer foot. They have decreased the foot by .08888 to 0039 inches. It is lower than the running area that goes around the kidney area. The elevated space that is between the outer foot and the valve plate will make it work much better. It will help out on the torque and volumetric to improve upon the unit.
Your part numbers will change on these blocks. You will no longer be able to get the old part number and they want be a service part either.
If you see a black square it means it is interchangeable.