65mojoe

+1 to twister...When i restored my 65 with an updated suspension, I started with all new kyb's then the 620 coils, then the 5 leaf reverse eyes -- I put the big 1 7/8? or so sway bar that Mustangs Plus sells. I didn't think the car could handle any better, then I put the rear sway bar in and it was even more responsive. People don't think you get much steering slop in the back since the physical "steering" of the car happens in the front, but I could TOTALLY tell a difference with the rear sway bar in. I would definitely consider adding the rear sway bar, it will definitely amplify performance (especially if you've already updated the rest of the suspension too).

jroseman

i have rebuilt the entire suspension, but with basically stock parts - except for urethane bushing. so adding the 3/4 rear sway bar would be a good thing for me?

65mojoe

Yes

Colorado_Mustang

Actually, if you have the stock diam sway bar in the front, you do not want a large diam sway bar in the rear. Your rear should be smaller than the front, 70-80% smaller is typical.

2bav8

With 4 1/2 leaf spring, KYB shocks and Cal-Trac traction bars I would hesitate to call the rear suspension of my car sloppy.
If anything, I would like to soften my rear shocks with a set of Konis for better grip (like I have upfront) but that upgrade will have to wait for a better budget.

I still stick my my guns that sway bars are a "tuning device". I would imagine most people's suspension setup is similar to what I used to run, stock control arms, stock or near stock sized tires etc. Back then I used to run a 3/4" rear sway. Was great for that setup, really was. Car was well balanced in the corners. Then I found a few upgrades that made the car handle exceptionaly well, far beyond the limits of the original suspension. However with the 3/4" rear sway bar the car was dangerously loose with the latest upgrades. Off came the rear sway bar and poof, a car that handled great and could be driven hard on the street or at the local auto-x events. Thus, my setup does not require the need of a rear sway bar. Your results may, and probably will vary depending on your suspension setup.

Think I'm still crazy? Check out a well known aftermarket suspension company called Global West. Now, I don't use their products (well, maybe one) but even they mention (repeatly) on their website that a rear sway bar is not needed with their parts. My setup is similar to theirs and as stated before, handles far and away better than the original suspension that came from the factory.

Just to restate, sway bars should be used to tune the suspension. That doesn't mean there are combinations that can't work well with them. My original setup worked well with one on a stock suspension. My modified setup does not need one. My $.04