Rear Sway Bar?
My sway bar is .125 diameter, which is much heavier than a stock way bar.
I assume you mean 1.125"?
It still matters what your torsion bar diameter is, and the spring rate of your rear springs.
Also, as for adding a leaf vs adding a rear bar, both will ultimately increase your roll stiffness. The biggest difference is that the sway bar will pretty much only increase the roll stiffness, whereas adding another leaf will increase the overall stiffness of the suspension. As I said earlier, the leaf spring stiffness in the back from the factory wasn't that far off even if you've upgraded to larger radial tires. Most mopars set up for handling are only going up to 120 to 130 lb/in springs in the back, factory XHD's were already 110 lb/in. Meanwhile, most of the torsion bar spring rates are being increased to 250-300 lb/in for the more serious handling cars.
All I can tell you i I love rear sway bars. I had a 70 T/A challenger with both bars (factory) and it handled like it was on rails. Best handling old mopar I've ever owned.
Just depends on the suspension set up.
Not as different as you'd like to believe. Front to rear weight bias isn't that different, same basic chassis construction, etc.
The higher front wheel rate is probably the biggest effective difference, which is what makes the addition of a rear bar a good idea. All in all, it comes down more to how the suspension is set up than A vs. E body.
