To do it right around $4500.00 in parts and labor. In a performance pleasure craft I highly recommend blower specific pistons with coated tops and skirts, HD tool steel pins, and I would get 10 pistons, never know if it burps and may hurt something. Min. order on custom pistons is usually 4.
You'll have to rebalance assembly.
I highly recommend coated mains. Just good insurance for an extra $75. Rod bearings and that is even better.
Blower specific cam with no advance. Lobe sep around a 112.
Good set of matched carbs from a carb modifier will make the most power, but since Holley came out with the HP series, they are quiet good out of the box.
Good reliable fuel delivery. If not, you can melt your bullet and loose crucial boating time.
Last but not least, dyno the thing and have it lined out before dropping it in the boat. May cost you $500. But that is cheap compared to what it can cost after a screw up.
Chris