What makes you think it's a Cafe? The deck is completely different from a Cafe (looks more like a Gun). If it's not a notched transom hull then it "may" be a Cafe hull. There was only 3 notched Cafe's built and they all had the cafe deck. I assume if it's a Cafe hull and has a shortened gun deck and short stagger it was purpose built (for racing) like the purple/black checkered flat deck staggard bullet. In that case I would venture to guess a very light lay up.

These are 450cid. The hull is not an old pleasure craft. It's an early kevlar layup. One thing I can say is that the first heavy guy to walk on the deck will have a big surprise and a bigger bill. There isn't much to this boat.

The deck was originally screwed on. She was a purpose boat, spent most of its life with number dots on the deck and hullsides. The deck is now molded in and the fairing is a "mod". It's not a full stagger.

A 350 engine can be bored and stroked to 454ci and maybe a bit larger. The SBC has limits to how big you can go before the crank and rods start hitting the camshaft. There is a full race block with a raised cam location but it's very pricey.
The difference between a BBC and SBC is the physical size of the engines and most of all the heads. BBC's have the canted valves while SBC's have inline valves. The bigger block allows for more room to bore and stroke it. The bigger block also allows thicker cylinder walls, main bearing webs and many other advantages. The early BBC was a 396ci and look what we have today.
The original BBC (1963???) was called The Mysery Motor. When it first appeard it was built for racing only. The great Smokey Unick still had the first BBC in his warehouse when he passed away along with many on-off parts like overhead cam hemi heads for the BBC and a set of canted valve heads for the SBC.

Nice looking boat/engines---have fun!