There is an ongoing debate about the track bar being required or not. But in my experience, it is required.
My set up includes a 2.25" Precision Metal Fab RSK and V code springs. For my own testing I removed the track bar....at parking lot speeds the steering felt vague and soft. Got up to about 35 mph or so and the front end was doing the death shake. I truly thought the front axle was going to come out from underneath. I returned home at a mall crawler speed and put the track bar back in. I don't argue with those that say it is not needed...maybe their real world self experiences say so...but for me, it is required.
With the 2.25" RSK, V code leafs, FD400 drop pitman arm, 2.5" drop track bar bracket and an adjustable track bar make for zero bump steer. Same drop pitman arm and a 3" drop track bar bracket was close, but not perfect.
If I wanted to debate...this would be my position:
If the factory D60 comes with a track bar, how is moving the fixed end of the leaf spring to the front of the frame, where it is weaker, and then extend the mounting point down 4 or so inches which increases its leverage, creating a better geometry that no no longer requires a track bar for support? And the rear leaf spring mounting point is now extended farther from the frame about 3" with a shackled pivot...further exaggerating the leverage the axle.