Hi graham
As it had water in it why not give it a damn good flush with fresh water
Then I would definately presure test the tanks, before doing any more to rig them for use.
If they leak the task to get them into use could be huge
If the tanks are sound you need a good filler and vent arrangement, plus a solid line from the bottom of the tank to an in line water and dirt filter near the engine. The flexible fuel line then goes from the filter to the engine connector.
POp in to see me at work mate and I can show you some examples