Good on'ya. No I don't but good on'ya. When the state gets its behind finally handed to them, I'm getting an Ace pistol with proper arm brace stock. I've longed for a Galil platform for a long time.
You need a gun shop with an in-house gunsmith, I would think. Off hand, I can't think of anyone. But if a dealer is regularly pinning stocks, I'dt think this is not much more than that.
I will not touch the Galil including the Galil Ace. The AWB says IMI Galil by name. IWI is the successor to IMI when it was privatized. The Galil Ace is a Galil. Net net I consider it an assault weapon regardless of any possible compliance work since it is named by name. Preban good. Post 13-sep-1994 not good.
I suspect you can find a FFL that will do the compliance and transfer whether through ignorance or through a difference of opinion on legality. You have to decide what risk you are willing to take. You could always ask @nstassel for a consult.