I bought a 30 footer for 500.00.....
Without seeing the boat or knowing how long it has been underwater, I am not sure how to advise you or even whether to congratulate you or not.
The boat in question was designed as an early IOR era race boat. By 1980 these were very obsolete as racers as boats like the J-30, Kirby 30 and J-29 had made these older IOR derived boats pretty useless for racing. Their cramped interiors and poor sailing characteristics made them less than ideal as cruisers as well.
In really perfect shape, these boats have a value somewhere between $15,000 and $20000 (but typically closer to the $15K end of the scale.) Once a boat has been this badly damaged, no matter how well it is rebuilt, it is worth something less than a boat that was never damaged. In this case, I would guess that if perfectly repaired and you disclosed the damage to the buyer (which I would recommend doing if I were you) the boat in perfect shape is worth maybe $10-12K.
When you look at what has to be done and assuming you do all of the work yourself, you could easily spend several times the value of the boat. This is no small project.
You have not mention sails so I assume that you will need new sails. New a set of sails for this boat would be close to $10-12K. Used they would be half to a third of that but you would no longer have a boat in perfect shape. This is a 25 year old boat so chainplates, mast step and associated suporting structure, standing and running rigging are beyond their useful lifespan. Depending on how long the engine was under water and what if anything was done when it was recovered you could need to do a top to bottom engine rebuild including starter, alternator, bearings, and valve guides etc. Given the cost of the parts for older Volvos replacement may be cheaper and if not pickled before now, then the engine may be beyond a rebuild.
You can expect to replace worn out or out of date deck, galley, and head hardware. You can figure that the upholstery, safety gear, and electronics are shot. You can expect to rewire the boat and replace electrical and plumbing system components that need repairs, upgrading to modern standards or replacement.
Besides the obvious damage, you can expect some blister, fatigue, displaced bulkhead, hull deck joint or deck coring problems. Replacing a keel without having an old keel for salvage value costs somewhere around half to 2/3 of the total value of this boat when you factor in shipping the keel. If the stove is pressure alcohol, it is probably not worth rebuilding even if you can find the parts. If it is propane the system needs to be rebuilt but that can be done. And that does not include the hull repairs.
All told this is a list of work that is close to $30K. Unless you are looking for a project and don''t care how much you spend on it vs what the finished boat is worth, my best advice is to cut your losses. Absent that I would advise to to carefully research costs, set a budget and stick to it.