Rear Sway Bar Question

The smaller the better. If the back end slips away from you, the rear sway bars will make it more difficult to regain control.

I used a Mustangs Plus 3/4" bar on the back of my '68 Cougar.

Definitely firmed up the back but as Caspian65 points out - the back end was easier to hang out and could potentially get away from you once the bar was installed.

You may want to look around at several designs to make sure they won't require your exhaust to be modified.

Installation was easy, but required drilling holes in the frame rails for the upper mounts. The mounting part quality was a little below my expecations and one side actually broke after a few weeks - metal bracket cracked. The manufacturer replaced the part under warranty very quickly and with no questions. I had no other trouble with it.

I did other suspension mods at the same time - heavier springs - big front sway bar - etc - so the 3/4" bar "fit" with the other parts I installed. If you car is otherwise stock I'd look at a 1/2" bar verses a 3/4".