By chance do you know if a '59 Pontiac spindle is the same as your '60? The reason I ask is because my '56 Chevy had '59 Pontiac spindles with '74 Corvette calipers and rotors. These had been installed prior to me owning the car and the brackets appeared to be a quality aftermarket part. I removed them this spring.
The spindles were identified by the engineer at Rare Parts as I knew they weren't '56 Chevy pieces but couldn't tell what they were.
If you are interested in the brackets let me know.