Hi,  I am in MI and just bought a jet boat.  I will post pictures soon and need help. 

1) Was told it was a 197? Cobra jet boat made in MI.
2) Was told it was a 468 BBC (numbers say it definitely started out life as a 2 bolt 454)
3) I took it out on the water and it will run 54 (Phone GPS) at 4500 RPM (I would like to get to about 6000 RPM with an "A" SS impeller at some point).  Was told it was supposed to have 400+ HP.  Per the pump curves it appears to be about 340 HP if it has an "A" impeller.  I definitely want to get above 60 MPH.  How difficult to get to about 80 MPH???  Of course I have a limited budget.
4) I cannot turn the pump by hand is this a problem? I disconnected it from the motor. New bearing(s) required? Complete pump re-build required?  What do I need to look for?  Packing is tight but still leaks possibly too tight or worn out?  I am sure there are posts on here concerning mechanical vs rope seals but looking for recommendations.
5) Pump is a Berk. JC No trim, No ride plate, does have some type of loader and not a rock grate.  Is it worth the upgrade to a dominator?  Is a ride plate a good idea?  It would help cure the transom plate issue stated below.
6) Impeller is probably an "A" aluminum. Guessing based on RPM and HP curves.
7) Currently looking for a 0 deg transom plate it is cracked and leaking almost as fast as I can pump it out.  I also just noticed that the transom plate hangs about a 1/2" below the bottom of the boat "V" in the corners (I don't like this and want to fix this too!).  Is this an indication of more "issues"?  Would I be better off making a transom plate out of Aluminum?  If so how thick of a plate do I need?  I have a Bridgeport and rotary table so I am sure I can make it myself.  Any concerns or recommendations for this?

Any help / information would be greatly appreciated.

Thank you,

Mark