I may be way off here but I don't know that it's worth doing. You're going to take the salt water use hit on resale even with the closed loop system. With diligent flushing and use of products like Salt-Away I don't see your engine's water jackets being completely rusted through anytime soon. You will probably go through water circulating pumps faster than a fresh water boat but those aren't very expensive either. Worst case you may need a GM short block for like $1,500 a few hundred hours sooner than you would have needed it with fresh water use.
So, my opinion is unless it's like a 2010-2011 or newer just add a flush kit, run it as is is and always flush/wash the boat thoroughly immediately after use. I've never run an inboard in salt water but I have a fair amount of experience running/maintaining salt water PWCs, outboards, and I/Os (None being Salt Water Series, all with open loop cooling).
Your trailer will suffer the most. You could try to maintain it but it will still corrode and fail within a few years. The actual frame and finish of the trailer is a problem but also all of the moving parts will likely seize up (i.e. brakes, suspension, swing away tongue, etc.) since it gets completely submerged and there are all kinds of places for water to hide. A better option may be to sell your factory trailer for a few thousand while it still has value (Assuming it's in good shape now) and apply the proceeds an aluminum trailer with SS brakes from somebody like BoatMate that will last indefinitely with regular salt water exposure and proper maintenance. The way I look at is is you probably have a trailer worth $4-5,000 now that will be near worthless in 2-5 years or you could cash that in towards an $8,000 or so trailer that would maintain it's function/value today.
As far as other things to be concerned with a lot of miscellaneous hardware and gear will corrode pretty quickly in a salt water environment. Things like your gas springs for hatches probably are not the SS versions. Keep them lubricated but just plan on replacing them with stainless equivalents when they become unusable. Keep your engine sprayed down with an anti corrosive spray before you go out and after you clean up. Keep your aluminum waxed (Tower, speakers, dash billet, etc) or coated with some sort of protectant that's safe for anodized aluminum.
That's about all I can think of right now.