(d) A credit union is authorized to act as trustee or custodian, and may receive reasonable compensation for so acting, under any written trust instrument or custodial agreement created or organized in the United States and forming part of a pension plan which qualifies or qualified for specific tax treatment under section 401(d) or 408 of the internal revenue code, for its members or groups or organizations of its members, provided the funds of such plans are invested in share accounts or share certificate accounts of the credit union. The plan shall provide for the appointment of a successor trustee or custodian by a person, committee, corporation or organization other than the credit union or any person acting in a capacity as a director, employee or agent of the credit union, upon notice from the credit union or the administrator that the credit union is unwilling or unable to continue to act as trustee or custodian.