Well SBT called me yesterday that they don't have it in stock and I'll have to wait 10 days to get it shipped. We'll get 1 more week of nice weather here so I decided to put it back together with the old impeller and fix it during the winter.
Some update. Took the impeller off and it looks ok for me.
Put it back together and gave it a test drive on the lake. It hit 62mph.
Now I'm thinking that something wasn't installed correctly the first time.
Yea, your speed is directly proportional to your RPM. Seems like you're missing a few hundred, and hence the slighly lower speed. My 185 GTX hit 58 as it's top speed. 59 if I stood up and farted really hard.