This act shall not apply in the case of wills, living trusts, deeds, or contracts of insurance or annuity, or any other instrument wherein provision is made for distribution of property different from the provisions of this act, or where provision is made for a presumption as to survivorship which results in a distribution of property different from that here provided, in all of which cases the provisions of such instrument shall be given effect.
Okla. Stat. tit. 58, § 1006