need help centering my diff??

[aany001]

This might be a stupid question but how do I know my differential is centered in my car (69 camaro). I have the DSE mini tub kit with a shortened 10 bolt and the factory perches cut off.Just would like to know where is the centre line for these diffs?? As of right know when I have the complete diff assembled with my disc brakes and 18x12 wheels installed in the car the left rear wheel is closer to the quarter lip than the right side by 3/4".From the back of the car you can really see the difference.I tried sliding the whole diff to the right approx 1/2" but I loose my gap between the left inner tire to leaf spring clearance.I have lots of space on the pass rear tire inner and outer!!! some body please shed some light on the situation!!! At least if I know that the diff is where it is supposed to be I can figure out my other clearance issues.

Thanks in advance.

Steve