Thanks - interesting that your car received the 12-bolt. I remember a yellow unrestored '66 327/4-speed bench seat Malibu that would park near my college dorm, and it did have a 12-bolt (although I never crawled under it to check for a Muncie).
This car has been relisted in the link below - still a neat and relatively scarce ride with these drivetrain options.
Link to 1966 Malibu Convertible auction