Hello 289Galaxie,What I did first was to replace the stock sway bar which I believe was 7/8" diameter (could be wrong) with an Addco unit. The Addco is a solid bar that's 1-1/8" in diameter and is quite heavy. The difference was absolutely night and day. Highway off-ramps that I was white knuckling at 40 mph I was now taking at 50-55 mph with minimal body roll.
After a year or so I replaced the Addco with the Hotchkis for no reason other than I wanted the Hotchkis. Wasteful I know but I sold the Addco to a friend so it took the sting out a bit. Although the Hotchkis bar is larger in diameter than the Addco, as you noted the Hotchkis is hollow therefore much lighter. I would have to say that I did not notice a difference in handling between the Hotchkis and Addco, but the Addco was already much better than stock. In my humble opinion, each one is leaps and bounds over the original but equal when comparing the two brands.
Keep in mind that not everything else is OEM. I'm running Eaton Detroit -1" springs at all four corners and KYB shocks but I also had that combination with the stock sway bar. I also added the PMT trailing arm kit with rear sway bar, albeit about a year after installing the Hotchkis.
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Thank you ever so kindly for posting the picture of your rear axle. I have a favour to beg, would you mind posting a picture of your rear control arms?
The reason I ask is I do not like the Hotchkis rear sway bar installation. I like the simplicity of a rear sway bar on the rear lower control arms like yours. I added a rear sway bar in a very similar fashion to my 1973 Caprice Classic which never had one nor does anyone make one for it. I am curious as to the shape/dimension of your lower control arms.
If it's one thing I wish Ford had the foresight to do was put in a triangulated 4 link rear suspension these 3rd gens.