The regular body style cars (62 series, DeVilles, Eldo, Fleetwood 60 Special) use a stabilizer/anti-sway bar that is about 13/16" in diameter.
The 75 series/Commercial Chassis cars use one that is about 15/16" in diameter and provide better anti-sway resistance when cornering.
Installing a stabilizer/anti-sway bar from the 75 series/CC in a regular body style is a great suspension upgrade. I installed one on my 64 Coupe DeVille a few years ago and could tell am immediate improvement in reducing body roll when cornering.
If you know of anyone parting out, or that just happens to have one of these thicker anti-sway bars grab it. You can then pick up the end link-kits for reasonble prices at many local auto parts stores such as Autozone ($18 a pair for part# SL90HD or at Kanter ($22 in current catalog). You can reuse the existing mount bushings where the bar mounts up to the frame if in good condition (it's a tight squeeze) or can pick up new mount bushings from Kanter and other places like Summit.
I've parted out four 75 series cars over the years and no...I don't have any to sell right now. If you see someone parting out one of these cars, I would recommend picking up the anti-sway bar if it is reasonably priced. For many muscle cars, you can find aftermarket anti-sway bars for these cars, but don't remembers specifically seeing these for the 63/64 Cadillacs. Perhaps some of these other makes/models will interchange? If so, please let us all know as these 75 series/CC bars are hard to come by!!!