Factory Rear Sway Bar

That's kinda messed up.
But I can certainly see why you might want a bar on that car.One word; airshocks. Joined by a Tee, right?
Up here in Manitoba, you cannot run your tires sticking out like that, and you will get a ticket,Pronto! And Teed airshocks will shuttle air back and forth between the bags and let the body rub.
The general idea of using a sway bar, you have completely violated. But I suppose if you're careful, you won't wipe out on every corner..
The proper solution for this car, is to put the wheels where they belong;inside the wells, ditch the airshocks and the bar, and set the ride height with properly matched and arched springs, with standard length rear shackles.And then to set the front ride height, and rear pinion angle.
But hey, whatever floats yer boat.
It actually looks sweet, I know, but, it's an accident waiting to happen.
I love the look, and did it to a slanty powered 69 Barracuda, which I drove very carefully,with N50-15 tires back there. I could not get into trouble.
My 74 Dart 360 4-speed,also with those same Ns? That was a whole nuther story.

BTW,on a streeter, a wide footprint is not necessarily an optimum solution. A longer footprint in the for/aft orientation with a similar area,will actually provide more straight-line traction. So if traction is a problem for you, going to a taller somewhat narrower tire, to fit bit into the stock well, is a no-brainer. And by getting the backend down, you will put more weight on the rear tires, helping street traction, and vastly improving cornering with the flatter running springs.. And as a bonus, that will take some weight off the front end, which will of course improve handling. 27 or 28s back there, is all you need, but the 28s sometimes require careful fitting. Mo money.................
Drive safe, take the corners wide, or slow down.