Oddball stroker question

I've searched around and all the performace marine crate motors for brand X use the Scat 9000 series so I'm thinking cast will be fine. I'm not looking to cut corners per se, but crap adds up when you have to buy 2 of everything lol. The damn exhaust manifods are 2200$ a set so that is 4400$ alone. I think I'm gonna run the Chineese air gap manifolds for both price, and the fact that the bypass hose and thermostat housing are in a better location.

As to the closed cooling there is a 5" round x24" or so long heat exchanger, basically a water to water radiator so the sea or lake water gets pumped up from the outdrive through the heat exchanger and out the manifolds. The engine is filled with antifreeze which keeps the inside of the block cleaner and when I head to the coast or Florida it keeps the salt water out of my motors. Plus it makes for easier winterization, just drain the exchanger and manifolds.