There is only one action and that is either a German made Varmintmaster action or a Japan made Varmintmaster.The bolt face will more than likely keep you from building a 223 on one of the Varmintmaster actions.The bolt face would have to be built up and then turned back out to the proper diameter of the 223.I guess a real good smith could do that,but it would cost a lot.Then you would have magazine issues with the smaller case of the 223.224 Weatherby mag and 22-250 would be your best shots at a rebuild in 22 caliber.
I've always wanted to rebarrel one with a 25 cal. barrel and chamber for 250 Savage or 250 AI and run the 80gr. TTSX as hard as it would go out of one.
I might provide you with a complete Varmintmaster and take the stock you have in trade plus cash.If you are interested,PM me.