Rear IRS Suspension Question

[Xellex]

I think EvilC referred to something else: mounting the Anti-roll bar from the Porsche to your bug requires cutting the brackets off the Porsche torsion housing, and welding them to the bug torsion housing.
You are going to need to add some material, because the anti-roll bar needs to clear the chassis fork.
In my case, the Anti-roll bar bushing sits at exactly 6,5cm away from the torsion housing.