Help! Dodge Cummins in boat

[SKAG]

I've been reading for a while the vast knowledge on this forum and finally decided to join because I could use some good advice/help. I have a 180hp 5.9 Cummins from a 1997 Dodge (CPL 2022, manufactured 2/15/96) in a commercial fishing boat. I didn't have the funds to get a new Marine Cummins and found an almost new motor out of a totalled truck. The motor has a custom water jacketed exhaust (pipe inside of a pipe) with the original hx35 turbo. A 4" stainless exhaust pipe passes straight up from the motor thru the cabin (no frills on this boat!). Instead of the stock air to air aftercooler on the truck, I found a jacket water cooler from a 250hp marine engine. The engine coolant passes through a pipe running on the bottom of the boat. The motor has 2500 hours on it and still sounds great. Last week my turbo began to make a lot of noise and I am now replacing it with the hx40 (found a brand new one on e-bay). Since I am upgrading the turbo, I wanted to take the time to possibly add a bit more horsepower - this is where I need the help. With the HX40 arriving, what can I do to this motor that will reasonably increase HP (say 30 to 50 HP) without compromising reliability? I want to be conservative because this motor runs under a continuous load - no coasting down hills! I've read all about the TST plate and other modifications, but not sure what the best solution for my application would be. Also, I am planning on insulating the turbo to keep the heat down in the engine room - I've melted a lot of things from the radiant heat - including my air filter - Does anybody out there know if insulating the turbo will do any damage to the turbo???

I know I don't have a Dodge truck, but I do have the best part - the motor.

Craig