Hi, I have started a rebuild on an old M440 for my dad's boat. Had the heads taken into the machine shop and they are rusted and pitted pretty bad from sitting for 20 years, does anyone know what valves I should run? Do I need Sodium filled, stainless, stellite, or is stock steel fine? I was thinking stellite for the exhaust would be the best option, but can't seem to find anywhere to buy them from. Since I'm here, I've got a few other questions too. In seeing the condition of everything I took apart, I was wondering what making this boat a closed cooling system would require? I would probably want to maintain the fresh water in the exhaust manifolds or heat exchangers though. And aside from the marine gaskets required, are there any other considerations I should be made aware of? Special distributor or pistons maybe? I've built plenty of car and motorcycle engines before, but this will be my first V8 marine build. I don't count the Mercruiser 4cyl. I did 4 years ago. I did ask the machine shop to use hardened steel valve seats and guides since I will be running unleaded, and to align bore the block and balance the rotating assembly. The old crank had a spun rod bearing and is toast, can I replace it with a crank from a car engine? That brings the next question, is this an internally or externally balanced engine? I know most of the car engines past 73 were external. Thank you in advance for the pool of knowledge I am about to receive.