Spacer Ring

Trying to figure out if the Spacer Ring, part no. 901 352 413 00 is supposed to be on my 66? I see it in the parts manual. But it's not clear what it goes on. I know it was on my 68 912, but my 66 did not have one when I removed the wheels. If it is supposed to be there from the factory, the next question is, if running wider wheels, such as 6 or 7 inch Fuchs, is it necessary? My car came to me with 7" BBS wheels and no spacer. Seems to me it's not necessary. Thanks

They made the track wider in 68 with the spacer. They also cut the fender lips. Not used earlier.