Because it is sunday afternoon and you have nothing else to do how about a discussion about engines!
Your preference and why

632 big block or 500 ci lsx motor.
These are the only 2 options sorry

These both would be turbo or procharged, about 10-12 psi max

from what I can find with my "research" I see that a small 500ci lsx motor can build the same power as a 572 or+ bbc because it is more efficient and it looks like they use less gasoline than the bbc from what owners of this engine have said, and this has my attention.

So what are the opinions.I am going to make this a real build with pictures so I need to get the base determined first.For every comment I will send you a $50 bill in the mail-
or not

i had 632 cuin with turbos in the bigyellowcat so I would vote that direction , you should be able to build them for 20-25 k

Even though I like the LSX and makes great power the cost of these builds is still pretty high from what I see compared to a BBC. I do like the technology of the LSX and to me seem like a stout foundation to build big power.

What hull is this going in?

38 foot catamaran, I like the idea of the lsx engines because everyone says they are so much more fuel efficient but make almost the same power but I can not find real world information that shows the fuel use between a big block and lsx block , as in a real world side by side test- apples to apples

NEITHER. The LSX engines are awesome...but you can do better for your application with a BBC. But I would keep the stroke at or below 4.375 to avoid windage. 4.5 bore is a 557, 4.6 bore is a 582. I like procharger under an engine hatch.

bbc for me.

A 38 Foot Cat, BBC for me.
A 32 or smaller cat, LSX for me.

I assume this is your ocean express? staying arneson, or going to 6's?

Yes this is the OE, the arnesons are gone now sold for 10k and there will be the #6 soon. replacing the entire transom.I dont know why ocean Express used so much wood in the transom but now it is going to be just glass and much stronger. Also I just got this message from a very reputable engine builder
i

"I would not do this with LS engines. The sure bet is to do it with the BBC's The 4.750 stoke is a bad stroke combination as it makes the piston weak. I would go no larger than a 4.500 stroke in a powerboat application with a tall deck. this will give you good rod angle and a good piston design. I also would only do it in a 4.500 bore for longevity this would make a 572 cubic inch engine. the 632 is not a good way to go with this."