They put in an extra procedure to the spline part of the block. These three groove identification measures will be put on there to let you know you have a new model. Other measurements on the block want change. The pumps want change, but your service kits for the block will have this procedure on the block for the pump or the motor. All fixed and variable motors will have this on it. If you have a black square it means it is interchangeable.
We can help you with finding 90 Series parts of any model. If you need your unit repaired or rebuild, we can do that to. If you need to buy or sell cylinder blocks call us at 662-871-8403.
tupelohydraulics@gmail.com