If the gear ratio is what you want, one can install a posi after ck'ing current backlash in several spots. Object is to recreate current backlash with the posi carrier, no reason to blow $400+ on the clunky Powertrax-units.
Let's use the example of .009 backlash, just re-shim to get close to .009, even .008 or .011 should be fine on a driver. Say the current backlash is loose from worn gears or loose pinion, say .024 or .028 backlash...really sloppy
, sucking the backlash back in to .008-.010 is not a good thing, as is, as gears have reestablished a pattern at that loose a backlash. Reinstalling pinion gear with new crushsleeve & setting backlash to .008-.010 will usually create a noise problem. Better to remove pinion bearing & add 1/1000th pinion shim, before bringing backlash in to say .012.
When installing new Eaton carrier or rebuilt !2 bolt Eaton carrier, consider the old side shims are not going to work. I draw from big stock of used side shims to pick a correct side shim for lh cap side, then use GM service spacer & correct thin shim on the right side. Without having a large selection of used side shims & a $100 selection of new GM thin shims, some times just easier for one time posi installer, to buy a set of Raytech shims or the wild interlocking shim stacks. either that or buy the GM Service spacer & mooch a side shim & ccorrect cast spacer off local r/e pro.