S type xk 3.8 in speedboat

[Jagboat]

JUST JOINED TONIGHT, HELLO.
I bought this boat a few weeks back, she won't turn, have a small amount of diesel in all ports after looking in with scope.
Last weekend and this weekend removed all ancillaries. Loosened bell housing bolts and she's nearly ready to come out.
I need to take engine apart and make an assessment of wether to re build or not once I see what's been holding her tight.
She got oil and no water in her, she had cooling water and antifreeze ( but a little low)
Maybe seized rings, or valves.
I would really like to get this engine going again, but as with all projects, I'm on a tight budget, and once you say Jaguar everything seems really expensive.
If I do have to re build, what are the, you must do this now type of things?
I won't have problems with exhaust, as I will just have short tail pipes from each cylinder straight out the back, PLENTY OF NOISE.
Any other thoughts, ideas, go to webshops for cheaper parts etc would be great.