The WJ/WG does not have a rear track bar. It's what is known as a "three-link" system - a pair of lower trailing arms and the third upper arm laterally constrained (by being a "A" shape). It looks like four links, but technically it is only three.
For what it's worth, I've worked through this on my WG and resigned myself that it is a combination of the geometry and the large tyres. I've gone as far as putting in polyurethane bushes on the lower rear and all new rubber on the upper, yet it still wobbles in the rear like the particular type of girls Freddie Mercury sang about - the ones that "make the rocking world go round."
Geometry is hard to explain in words, but if you think about it, the rear ball joint is up high on the diff housing. When one wheel moves up the ball joint will want to move in an arc centred on the ground half-way between the wheels. This is a fairly long radius, so a small change in angle of the rear axle relative to the vehicle body produces a noticeable sideways movement of the rear. Taller tyres will amplify this because they make the radius longer.
I've gotten used to it and don't notice until I drive my hot-hatch for a few days and get back into the Jeep.