the Ruger Charger is a pistol from Ruger that uses the 10/22 action. he is wanting to put a Rossi Ranch Hand type stock on it. the Ranch Hand is also classified as a pistol. now whether it will work or not is the million dollar question, as to hwo much work and modification it will take to complete.
this is not legal advice or to be taken as such, but i think legally it can be done. using a pistol stock from one firearm to another pistol.
but i would suggest contacting the BATF for further advice on this to CYA.