Then your task won't be too hard at all, simply replace the bad engine long block assembly with the newer one. I suspect you will not be in salt water (Ohio) so your stock head gaskets and freeze plugs will work, but if you wanted to be safe you could pop them out and replace them with brass parts.

Cam profile may be slightly off, but I have used truck engines in boats with good results. All in all, I don't think you could go wrong.

BTW. you need a marine carb, not just any automotive carb. You also need a marine starter, alternator, distributor, and fuel pump. Otherwise you run the risk of a serious explosion, or at the very least, the wrath of the Coast Guard, if you are boarded.

Good luck.

Don