I am no expert,,, but pickling means that when the boat was hauled out the motors were drained and filled with kerosene or some other anti-corrosion fluid to help preserve the bearing and engine internals.
Secondly,, since the boat sank,,, all the engine accessories will most likely be locked up, I.E. alt. starter, and the control cables most likely frozen and need replacing.. Its a hell of an undertaking and have to decide if its worth your time and money. sounds 10 k plus another 10-15 k mininum for engines, controls and misc. plus your time. If you were really interested in a Pachanga, I would look at the used ones for 25 that don't need much if anything..
If they gave you the boat for 5 k and it took another 10-15k to repair I still would rather spend an extra 10 k and have one that didn't have any issues..
P.S. Alpha drives are not a good choice for big blocks either..