To answer your question after you get the truck lowered measure the rear end to the frame to see how far the rear end is off set from the center of the frame. (I would not rely on measurements to the body too many ways for it to be incorrect) The adjustable track bar is used to correct this problem. If you rear end is centered still then you won't need it.
Scroll to post 511 on the link and you can read my posts on installing a track bar and centering it.
https://67-72chevytrucks.com/vboard/...698377&page=21
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Thanks to Bob and Jeanie and everyone else at Superior Performance for all their great help.

RIP Bob Parks.
1967 Burban (the WMB),1988 S10 Blazer (the Stink10 II),1969 GTO (the Goat), 1970 Javelin, 1952 F2 Ford OHC six 4X4, 29 Model A, 72 Firebird (the DBP Bird). 85 Alfa Romeo
If it breaks I didn't want it in the first place
The WMB repair thread
http://67-72chevytrucks.com/vboard/s...d.php?t=698377