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If your getting water in the oil pan thats going to be a pinhole intake manifold gasket leak or a pinhole crack in the block.
The reason you do not see it when running is because the heat of the engine and engine oil is vaporizing water as it gets in there in real time. When the engine cools and the heat goes away, the water starts to pool then.
It's not the exhaust manifolds, if it was water would fill the cylinders and hydrolock the engine.
Thats that your looking at. I would re-do the intake manifold gasket, and carefully inspect the manifold itself for cracks when it's off and put it all back together and hope for the best. If you still get water after that there is a problem/crack/rot in the engine block.
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Yes as long as you get the year right. There are basically 2 generations of the 302. 1980 to 2002 is one generation, pre 1980 blocks are different. If your block is the 84 you said it is, then any automotive block from 80 to 02 would work as a core.
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They have different gasket kits for the marine engines.
Now if you have a heat exchanger with antifreeze, and this is a closed cooling model, you can use automotive gaskets, that is not problem.
But if you have just your basic raw water cooling, where sea/lake water circulates through the engine, then you do want to use the marine gaskets, the automotive gaskets would not last.
What's the difference between marine gaskets & automotive?
Sorry for the delay, had to run out. We do this out of our houses on the side, and do not work in some office for Justanswer.
The biggest difference between marine and automotive gaskets the amount and the kind of metals inside of them.
Automotive gaskets can afford to have things like iron and copper in them, because antifreeze is non-corrosive. Marine gaskets, if they circulate seawater through them, would rot in a heartbeat.