At least you don't have low-drag calipers--the big hang-up with the "NBS" master cylinder downgrade.
Is there something actually wrong with the master you have? If not, there's no point to changing it. The so-called "NBS" master is not much of an "upgrade".
What is the bore of the original master cylinder? How does that compare to the bore of the "NBS" master you intend to use?
If they're different, you can expect the brake pedal to react differently based on the difference in fluid movement.
If they're the same, you've gained--or lost--nothing except for the waste of time, money, effort, and enthusiasm.
