Looks like you have a 351 that would come stock with this boat.
The length of time since it has last been run determines how best to deal with it. If its more than a 6 - 8 months, fresh fluids, filters (don't forget fuel filter) & plugs and you are ready to fire up.
If longer than that, I would pull the spark plugs and pour an ounce of motor oil into each plug hole. Then get a large 1/2" ratchet and the appropriate socket on the crankshaft pulley and manually turn the engine over a few times. Then change fluids and filters and screw in the new plugs.
Make sure you are supplying water to the engine while running, but DO NOT TURN ON THE WATER UNTIL THE ENGINE IS RUNNING. If you turn on the water before you fire her up, you will end up with the water pressure backing up through the exhaust and through partially open exhaust valves and into the oil pan. Getting that oil and water mixed together out of the oil pan is a pain in the a$$.
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