I have 16" Fuchs taken off an '86 Carrera, allegedly 16x6 up front and 16x7 in back. I've got Yokohama AVS ES100's mounted, 205/55ZR16 flavored.
The rear fenders had been rolled a bit, and that wasn't enough to clear the 225s the PO was running there. I haven't had the car back from the shop a week yet, but I'm still seeing some rubbing when braking and turning on the switchbacks up in the Berkeley hills. So, seems we really did need to take the spacers down a bit in front...
I haven't taken the wheels off to verify the sizes, but if the above is correct than the fronts have an offset/ET of 36mm, and the rears of 23mm. Here's a link that lists a lot of info on the factory wheels:
http://members.rennlist.com/911pcars/WheelWts.html