If you measure the actual width of the rear guards, from the tub out, you will almost definitely find that they are different one side from the other. Likewise there should not be a difference in the fore and aft position of the guards but the fact that there is does not surprise me greatly. The joys of ownership of handbuilt cars, particularly when they are built in a workshop where a good number of components are fitted and placed by eye instead of using accurate jigs.
Agree that every car is different because they're handbuilt. You wouldn't even notice that on my car there is a slightly larger gap between tyre and wheelarch with standard 165's if the gap wasn't only about 12mm. I wouldn't consider increasing to 175 width on my car and only have approx 7mm clearance between tyre and wheelarch.
