Rims

Here is (hopefully) a definitive way of differentiating between Fuchs 8" and 9" x 16" rims.  These rims were fitted as standard to the 930 Turbo.
There is very little visul difference between the 8 and 9 rim, even with the 2 side by side (9" on left 8" on right)

Both have the same 1" rim flat and slope length

Look carefully at the wheel nut mounting, the 9" countersink is set lower in the forging
 

To be sure what rim you have, you need to look at the back As with all Fuchs rims the part numbers are stamped on the back, along with the little fox's head
9: 911 362 119 - ET 15 (the offset)  8: 911 362 117 - ET 10.6

Have a look at the mounting face, the 9" rim has an eliptical mount, the 8" is more triangular.

The mounting faces also show the different offsets