Your new stainless manifolds don't appear to have any place for the cooling water to enter, nor any place for the exhaust/water to mix before it is exhausted out the back. What is your plan here? I know nothing about marine diesels and very little about diesel in general other than the basic operating concept, but is this safe? It seems to me that without the exhaust being water-cooled they will get extremely hot. How do you plan to exhaust this very hot air?
This is a fascinating project though. I hope you get it all figured out. I've often wondered why the big v-drive's don't come with a diesel option.