Ther is a marine conversion ls thread buried with a lot of good info...

I had 88 22 with a bravo, no steering, 502 535hp, cmi headers and it ran 88 mph on gps back in the early 90's. you had to drive it but it ran like hell. you will just fine if you decide to go with a big block. good luck with the build and nice boat, one of my all time favorites

No big block, far too heavy and deprecated. Big inch small block will be easy because of the parts availability.
An LS would be my preference, fuel injected, refined, awesomeness! But expensive...

Drive Removal
Removed the drive this afternoon. Also picked up six sheets of 1/2" marine plywood. Still need to locate a local fiberglass supplier, but I may end up ordering the fabric online. Id like to be able to take out the transom and have it rebuilt by the weekend.

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Order your glass stuff from us composites.

I'd build a wicked stroker small block too!

Yeah you can't deny the technology and cool factor of the LS platform. I had a ERL 370ci motor with a modified precision 88mm turbo with billet upgrade making 1,200 hp. The ERL blocks are the best of the best if you know LS stuff. They re engineered them the correct way.

The only thing I don't like about factory LS blocks is the bottom portion of the block rails that hang too far down creating excessive windage. These aftermarket companies remove this and install a custom oil pan. But in a marine motor it isn't at all a deal breaker. If I build another motor next year it will be a large CI LS for sure. Looking forward to seeing your build progress.

Been researching the LS engines, an LS1 or LS2 can reach my power goals pretty easily. I may end up putting in what I have now to get me going, but I still get a bravo before hand. Hardin Marine has some good options for LS exhaust, both manifolds and headers! But at $4k the headers would need to be an upgrade afterward. Due to the expense in any case, an LS and hydraulic steering may be a few years down the road.

Transom
Got my glass in last Monday, decided to wait and start until the weekend. I built some clamps to help press the boards to the back of the hull, still need to run some supports for them. I'll also make some bolt holes where the exhaust and drive protrude so I can clamp those areas as well. The transom removal took a lot longer than I anticipated, nearly a whole day. After it was out I ground down the extra glass. I left off today with fitting the first board, I think I'm going to glass them in one at a time. Seems easier than trying to monkey around 3 laminated together and clamping them in, though it will take longer. Hope to get them in this week and start on the stringers next weekend.

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An LS1 or LS2 won't see 650hp. Trust me you want cubes. As stated, I've toyed with some large power LS motors. Toss a turbo or blower on it, then it will rock! Even a 6.0 or 6.2 LS(N/A) isn't gonna have the torque a BBC has. Everyone gets so spun out on HP, when torque turns props and is the most important value. There's a reason LS motors aren't the big thing in marine applications, they are expensive and don't offer large displacement. Not dogging the idea, I like it, but for a lower power goal naturally aspirated. Interesting to see what you end up with.

Supercharged for sure. Thats one of the main reasons it'll have to wait, need to build it as intended the first time. Origionally i was looking to build a blown 383 sbc, but theyre very dated and heavier. Until then the SBC on hand will do.

Just my .02 but full hyd. steering should be at the top of your list.

The little velocity's don't need torque.

I'll take a 525HP at 5800rpm small block any day over a 525hp at 5200rpm big block In a little, lite boat that responds to everything and anything.

A low-mid 300hp 'nothing' small block will go over 70 in one of these boats. That should tell you.