All RB water pumps are the same, RB30, 20, 25 and 26. There are two options available on the aftermarket side. The difference between the two is one, you will have to leave out a bolt on some engines, another is that it bolts straight up with no bolts left out.
Either water pumps will work and will not cause leaks or any mechanical issue if installed properly.
Genuine parts is preferable and yes Kudos Motorsports are great for them. But in all honesty, I work with RBs on a daily basis and there are no issues with the 10mm locator bolt left out. There are no gaps and the face of the water pump overlaps the bolt hole, creating a perfect seal.
All 4 of my cars with RB engines don't have the locator bolt. All running aftermarket pumps with no problems.
Part Numbers:
GWP898 - Gates
PWP898 - Protex
7054 - GMB or ACE (both Jap brands)
With water pump 898, you need to leave out the 10mm locator bolt. 7054 has a elongated hole which allows the slight offset of the bolt hole to fit on compared to the 898.
Send me a PM if you have any further questions. I can also supply timing kits as well.