After sitting so long, get up and running for a while and see if the rings start sealing better and compression comes back up. If not, do a cylinder leak down test to see why it's low. Could be the head/valves, could be the head gasket. Any of these would just require removing the head to fix. It could be the rings which would also require removal of the head and engine to do a complete rebuild.
Just get it up and running and see how it runs and acts.
Good luck.
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OK, I'm over it. Where's the beer?