If you want bar, it'd be better to use a Watts link. A panhard bar pulls the axle sideways, as Opticon mentioned, when the suspension travels. That's why Jeep Grand Cherokees with front and rear solid axles drive so crappy. Every bump and the body moves side to side. Maybe you'd get used to it but, it gives me an uneasy feeling everytime I have to drive one at work. With leaf springs, it's unnecessary.
A Watts link allows the axle to go straight up and down while locating it side to side. One downside is a bracket to mount to the center of the differential housing for the center to pivot on. Most factory ones have a cast aluminum cover it bolts to, some a heavy bracket bolted to the axle.
An alternate method is mount the outer ends of the bars to the area of the spring plates instead of frame brackets, and mount the pivot on the chassis. You'd need to fab a heavy bracket to go between the subframe rails yet be low enough to put the pivot point roughly in the centerline of the rear axle at rest. Not really ideal but, it does work.