Borax isnt a preservative, its more of a "bug Proofer" than anything
Huh? Borax has been used for preserving animal parts for years and years. It also has some ability to repel bugs, but that is not why it's used. Salt will pull out moisture, and make a stinky mess. If there is any tissue on or in the claws, you need to get rid of it. I would guess they still have tissue inside and it has to come out. Then apply borax and lay out to dry.