Here's how mine is done, for your application just ignore the header control valve and go with the rest of it, oh yeah you'll use one of your T-stat lines as header water, the other will be an overboard dump.
Here's the pieces you'll need for where the water goes into the engine, where the water pump used to be:

Here's some of the pieces you'll need to connect your hoses to them and the thermostat housing:

You'll need one of these TEE fittings for your headers:

Most importantly, buy good quality hoses & clamps, the shit from Auto Zoo and Poop Boys doesn't hold up very well. I used Aeroquip hose on my boat. Oil, gas, chemical & UV resistant.
Have fun!
PS- I have a good local hook up for the hose & push on fittings, adapters etc.