Mike,
That is not a C3 but a C4. The C4 hub bearing carrier is full floating where as a C3 has a trailing arm.
Your differential cover should be aluminum with the so called Bat Wing. Your's does look narrowed I think. It also looks as if your upper shock mounts are moved in quit a bit. You may want to try and move them outward.
C3
http://www.acp-euskirchen.de/zubehoer/c3_achse1.jpg
C4
http://www.scottiegnz.com/irs-front.jpg