Just as a WAG , probably about 75% if time and cost weren't an issue. Some of those airframes are probably pretty bent up, but if you started consolidating parts onto the best airframes, you'd get most of them together. You'd never get 100%, but certainly a majority.

The real question is if it would make any sense financially or strategically.

I've actually worked on (civilian) aircraft that were being pulled out of a similar graveyard in California. The real issue is getting the aircraft inspections done (particularly for corrosion) and the paperwork up to date. This can take months and be very expensive even by aviation standards. It's a lot more than just kicking the tires and lighting the fires. I'm sure the guys there work hard, but it just takes time to catch up.

From the operations side, the issues can be simple or complex - mostly involving the training of the pilots or requirements for new equipment that didn't exist when the aircraft went into storage. Different submodels of aircraft can have wild differences in cockpit setup, and pilots used to flying the "modern" aircraft don't know what to do with a bunch of old "steam gauges" and no GPS. Not the pilots' fault, they just would need retraining (which costs time and $). Other operational issues can crop up too - the servicing equipment might be different, for example.

And then in the end when you do all this stuff, you've still got a xx year old aircraft with old aircraft problems. You've also possibly got something that is easily militarily outmatched by newer versions. I love the F-14, but I wouldn't want to put one up against a F-35 or equivalent.

So could you? Yeah, possibly. It just probably wouldn't make sense in most cases.