Marine service is a completely different animal from most other uses. You've stated you'd like to get 2500 hours out of the engine, and I'd like to share a few reservations I have with some of your combination.
In my experience, longevity is reduced faster than power is increased. Getting 2500 hrs pushing a deep V is a big challenge. To get 2500 hours out of "hopped up" engine is unlikely. You'll have to decide whats more important, reliability/longevity, or a few extra knots.
Compression probably shouldn't exceed 8-1. You may find you need to fuel up somewhere that has no choice in fuel, and it may be a long trip @ 8 knots to keep it from hammering. The combustion chamber isn't known to be detonation proof.
Save the money you were thinking of spending on roller parts for the valve train. The rocker arms might last, but are not neaded in a low RPM engine, and the life of roller solid lifters at low RPM is pretty short. As failures on the water can be as bad as a failure in the air, you should keep it simple. In years past, even hydralic lifters were frowned upon. My own boat is 45 years old, and the original engines had solid lifters as do the replacements.
Forged pistons are a very good idea, and most marine engines had them. You never know when that plastic bag or piece of weed clogs the cooling intake and if you aren't staring at the gauges at that moment detonation will be the wake-up.
I'm with some of the others that a forged crank is not needed as the cast crank is very stout. My choice for a cam would be a solid lifer marine grind, although I don't think it would meet your 3K peak torque desire. I also have reservations about increasing valve size. At the RPM you are going to run, measurable power increases will be low, and as the exhaust valve depends solely on getting rid of the heat it's bathed in by transfer into the seat, the larger the valve, the hotter it'll run. Sodium cooled stems will help.
Good Luck
