I have one of these tricky setups in my race car. Its an L300 rear assy disk brake rear with 2 ratios 4:6 and 5:3. The centre is L300 with minispool. The way the minispool has been setup is that it has 2 Porsche 930 turbo CV's bolted together and then bolted to the crown wheel.
In the middle of the CV's are ford 9 inch 28 spline axle carriers.this allows for the axle assembly to be cut and shut to achieve around 1.5 degrees negative rear camber.
I can attest to the the hugely increased grip in the rear as opposed to the standard H165 I was running. I high speed corners it eliminates rear end twitch in mid corner.
The creator (John Taylor) of this setup told me it cost over $4500 to get done. It unbreakable in the surrent setup thanks God, as I dont want to ever fix it!!!
For the street I wouldnt bother, you are just simply not gonna push the car hard enough all the time to notice the difference.
If you are really keen on doing this, the poor mans way is to rune a weld across the top of the axle carrier and the cooling process will bend it like a banana until you get your desired camber. Otherwise do what b310GX suggests it sounds like a much more accurate and cost effective idea. If you are doing track work and its under $500 to do it...get it done, makes a big difference to rear grip