do not try to use an auto block. Cam has to be changed to lower you max torque curve. If you are replacing this and use the vortec block and have a 2 barrel carb. you will have to go to a 4 barrel carb. and manifold. If you do not the engine will only be able to run a very weak 3M RPM. It will starve for fuel. Valves are bigger and needs more cfm to run. Call Jasper and give them the specs. on you engine. They have a marine division and can get you a reman. engine block and you might be surprised on the price of a 6 banger. Do it right. You have to pay to play.