SBP 14-inch Steelies

It goes by brake size. 9 inch brake cars came with 4.5, 10 inch and disc came with 5.5.

Incorrect statement!
My 1967 Barracuda Commando 273 4 speed non-Formula S came with 14" X 4-1/2" wheels and 10" brakes all around. In 1969 I went to a dealer and bought new 5-1/2" Formula S wheels. They were standard equipment on Formula S cars and I believe those ordered with HD suspension.