Sorry for misinterpreting which side is the problem. My "summary" is the same except that instead of the ring gear pulling away from the pinion, it would be pushed harder against the pinion. That's still not good.
I agree with the other guys that an improperly assembled CV joint locks together and you can't make it move in/out and nor can you make it pivot. So it would seem to me that an improperly assembled CV couldn't be mounted because the the axle needs to pivot in order to allow the CV to bolt up with the trans output flange?
The fact that one wheel is sticking out and the other is pushed very far in seems like the bent trailing arm is the issue here. The wheel pictured appears to be a 16x8 (because the lug nuts are not countersunk) and usually fills out the SC fender flare quite good. On the left side the wheel is sitting quite far into the wheel well. So I think the trailing arm is sitting too far inward on that side.
http://forums.pelicanparts.com/porsche-911-technical-forum/936175-rear-wheel-position-mystery-911sc.html