I have some large schematics (A0 size) but they are not particularly helpful. For boats this age a lot has usually changed!
For the sedan models fuel tanks are 4 total 1000 gallons if original. Two outboard of the engines, and two transverse at the aft bulkhead in the ER. The ones outboard of the engines are likely rusting or will have already been replaced. They were steel (5/32") and the issue was the ER vents with vertical louvres allowed rain to enter. Rust developed on the lower edges of the tanks near the hull. It typically took about 30 years for them to rust enough to leak. Replacement involves removing engines etc, and that is the ideal time to do other stuff as there is great access.
Water tanks are typically two, one about 200 gallons in the lazarette abutting the ER bulkhead, and one below the master stateroom sole on centreline of around 80 gallons. The latter will sit in bilge water (if present) and develop leaks at welded seams that are prone to being submerged. This tank is best removed by cutting away a part of the forward ER bulkhead. Just the part between the stringers. The tank can then slide aft, into the ER. When installing a new tank it can be made a little larger (longer).
Here is an old thread that you might find interesting. https://www.trawlerforum.com/forums/...1-a-25948.html
If you have any specific questions, just ask away!