Re: 2.5 versus 3.0
I dunno if the blocks are the same - I suppose they are the same casting originally so it could be done but not sure if any clearancing needs doing for the 3L crank.
I know the crankshaft on the 3.0 is externally balanced so all internals from the 3L would have to be used. How long did it sit with water in it? If there's any crankshaft left- might be all rusted. And you're going to want to put rings and such on probably. Once you price a 3.0 rebuild/gasket set at $500+ and price the machining work at another $300, you might as well just buy a reman engine.