Re: Engine swap
I've done this several times without issue.
If the engine is saltwater cooled you will need to replace the following:
Freeze plugs
Head/manifoil gaskets
Circulation pump
Camshaft
Distributor, starter and alternator
Carb
Exhaust
Raw water pump
Thermostat and housing
Those are the main things.
Some say the marine engines have forged inernals and a different cast, I've only rarely seen this on any of the engines I've worked on, and as there is no saltwater anywhere the oil goes, the only reason for forged parts would be to strengthen the engine, wich is fine, but not really necessery to make it work. Same with stainless valves.
If the engine is freshwater cooled there's no need for new frost plugs, gaskets or circulation pump (unless it has connections for heater), as saltwater will not enter the engine.
Camshaft, distributor, starter, alternator, carb and exhaust would all need to be replaced, and heat exchanger would be added.