OK But what design specs?
John, unfortunately text on forums has no tone so please understand that I am NOT trying to be a smartass here; but to what specs are you referring?
The number of layers of glass in the keel stub and directly aft? Are you referring to the resin to glass ratio in these areas? Deflection under load?
This doesn't look like a catastrophic hit. The person doing the repairs will likely find some cracks and possibly some delamination aft of the keel. The compressed front nut may be from the hit or it may have simply been over-torqued at some point in the boat's life. Some exploratory grinding will determine the extent of the damage and necessary repairs. None of us can fully diagnose the necessary repairs from photos on the Net.
Those repairs should be in line with bringing a lightweight coastal cruiser back into safe operating condition and it really is a judgement call on the part of the person doing the repair. There isn't a "spec" for this and there may not be a single "right" way to do it. In fact there's usually more than one way to fix things.
Jim