Rear Sway Bar - opinions please

As a number of you may know I am in the process of restoring my 2nd J code 429CJ Cougar. both of my cars were built 4 days apart and are in the 3-4th week of october build date periods.
Both cars have a 1/2 inch rear sway bar. The car that I am currently working on still have the correct N cas/ 31 spline axels, and original 429CJ drive shaft and C6 transmission so I have no reason to suspect a switch.

Do you think

1. Cougars with this drive train received a 1/2 bar while the Mustangs received a 5/8th?
2. There was a production shortage at that time and the 1/2 bar was substituted?
3. The Bars on both cars have been replaced over the years.

Opinions please -

Thanks Mitch