Just to cover the IRS camber post...
I ran IRS arms swapped over side to side and found I could only just get 0 camber on the rear wheels with the car being absolutley on the floor! Otherwise you ended up with positive camber (not good ).
You can adjust the camber on the rear suspension by simply loosening the 3 bolts which connect the spring plate to the rear arm and move the arm up and down. Up will give you move negative camber and down will give you more positive camber. Remember just the 3 bolts which hold the spring plate to the arm.
I'm sure you've all covered this.. just saying it in different ways
Re - adjustable inner mounts for IRS arms. It's only worth doing with coil overs and you must move both inner and outer suspension points up as one or you'll end up with the most horrible suspension geomtery imaginable.
You can see this on the spring plates of Porsche works race 911s.
MG