I have had two of those at one time. They require massive lock work to become functional. I wound up tossing most of the lock parts and using some odd parts that I had to eventually make them work.
However, your question is how to fix the stocks. I have seen worse stocks repaired. First the big breaks. You will need some stainless steel bolts. Cut the heads off the bolts so that you now have a stainless steel reinforcing rod. Drill oversized holes in both sides of the break so that the rods will fit in the holes and you can put the broken pieces back together. Once you have it so everything fits together like you want, it's time to get out the epoxy, you want the slower curing epoxy instead of the 5 minute type, that way the epoxy will soak into the wood a little better. When you mix the epoxy mix in a little paint with it so the epoxy color will be close to your desired color. Put the pieces together, use rubber bands or whatever you have to hold it. Make sure to fill the drilled holes so the reinforcing rods are fully encapsulated. Don't mess with it for 24 hours.
Smaller breaks can be fixed with Gorilla glue. The nice thing about Gorilla glue is that it expands as it cures and fills in some missing spots. The thing about Gorilla glue is that it needs moisture to cure. So brush tap water onto the breaks before adding the glue. Don't mess with this for 24 hours. There seems to be some big pieces missing. Depending on your skill level you can either carve a piece that will fit and use Gorilla Glue to hold it in or you could use Plastic wood. The plastic wood is best used in multiple thin layers, let them dry completely before adding more.
Finally you will have a stock that is back together but has lots of ugly glue marks. Now is the time to file and sand back to the original levels. On the pistols that I had I just spray painted them black since the wood wasn't worth much. A spray coat of paint and a coat of wax and they will be as good as they ever were.
With patience you can fix them. I suggest you fix them one at a time. Fix the least damaged one first, learn from your mistakes and then work on the other. Good luck