Any production action will require extensive work to bring it up to target standards. If you want to start with a Model 70 action and then pour several hundred dollars into for truing and accurizing, I advide you to start with a Montana Rifle Company action. It is a clone of the Model 70 (but significantly better made), and the accurizing work is already mostly already done. The prices are very reasonable.
http://www.montanarifleco.com/Long%20actions.html