ooo new motor also has felpro rubber gaskets not cork thaughts guys?
If you're talking about the valve cover gaskets, it really doesn't matter (I prefer cork, but that's just me).
The different tolerences is required because of the open cooling system (cold lake/river water running through a warm block with hot pistons & heads).
Most important is cylinder wall clearances so you don't score or stick a piston. Rod/Main bearing tolerances are run a little looser due to the constant high rpm that a marine engine is subjected to (how often is the big block in your truck run at 4500rpm+ for 5-10 minutes straight?)
If you're willing to go through the work of changing the engine several times and are willing to wright off a new engine if it fails... go for it.
And like SuperJet noted, be sure to get some heat into the engine before you stab it run the sh!t out of it.
