After lots of searching and investigating several options, I decided to have some shims made to tighten up the tolerances for the TrackFinder install.
The original thrust washers were 2.1mm, with spacer/pinion shaft clearance of about 0.85mm.
Max spec clearance for the locker is 0.5mm.
2nd torn down diff had similar clearance as the first, but with 2.0mm washers.
So I got some 0.7mm 316 stainless shims laser cut, to use with the 2.0mm washers but in the ORIGINAL diff, gaining me 0.6mm overall each side.
It's now all within spec, assembled and ready for install <img src="/forums/images/graemlins/smile.gif" alt="" /> Just waiting for my pinion bearings to be pressed on the 5.38 gearsets.

Long a$$ 2000 Sporty, auto, 5.38 gears, TF front locker, 4"+ front lift (Kings +40 springs, 50mm spacers, 1.5" diff drop), TJ 104 rears 3" + 50mm coil spacers, 1.5" body lift, 31/10.5r15's on 15x8 Kings (ET-13), WARN manuals, Smart Bar, spotties