I would think parts would be available...You would have to go to a regular machine shop to get them....I get all my stuff from mine...

I don't know if you could get suff like that from jegs or summit?

I would try to find out why the engine has two detonated cylinders? If it had a problem in the boat chances are it would have more of a problem in the car....

If the engine was designed and built for the water (boat) the cam will have a higher LSA which will cause higher cylinder temps.... a cam swap will probably be in order.....