Mont. Code Ann. § 70-20-315

All deeds to real property executed prior to January 1, 1983, in this state or any state or territory of the United States, provided no action is pending on October 1, 1983, to set aside any such deed, which shall have been signed by the grantors in due form, shall be sufficient in law to convey the legal title to the premises therein described from the grantors to the grantees, without any other execution or acknowledgment or witnesses thereto whatever; and such deeds so executed shall be received in evidence in all courts in this state and be conclusive evidence of the title to the lands therein described against the grantors, their heirs, and assigns.