Was able to purchase a Briggs & Straton NOS (dated 1974) locking unit with two keys from a member on this site. Just got it installed today and it works great.
As I am new to working on a 69 GMC Suburban rear lock setup the drawing and information were great help. Thank you for posting the pictures.
I will say that it would be great if the two front door locks and the rear lock were keyed alike. Is this possible?