A body sway bars

I believe the original poster has a 73-76 A-body.

I helped fit the Hellwig prototype 73-76 front sway bars. They are offered in 1 1/8” . They also offer a 1 1/4” tubular (lighter, but more $$) not listed in that catalog

Like was said, the difference is in the hardware. For 73-76 A-body the K-frame bracket bars need to be special to accept poly bushing and u-straps. Also the 73-76 sway bar carefully threads though the K-member. When it’s thicker, it’s very important to get it fitted correctly.

I also have an old addco 1 1/8” and you have to make 1/2” spacer bars. And they won’t be as wide as they should be. Also you’ll have to shim/washer a lot to avoid rubbing.

Hellwig also offers an adjustable rear sway bar. Not listed in that catalog.

I also have a 73-76 Hotchkiss front and adj. rear setup. They are on my Barracuda now. Very nice, very detailed. But more $$