I've ran ours in the salt for years (pre rebuild) and have never had a problem other than the water splashed on the chrome headers would burn onto them. That and the salt that got splashed on the starter made it so I only got 3 years out of my cheapo Schucks starter.
With all that said, I haven't had the nerve to run the new setup in it yet but given we are 2+ hours from fresh water versus 5 minutes from salt water, I know next year I will......