They are on Ebay all the time. Most people call them C2 cup wheels. You might try germanautodismantlers.com. I was there just before Christmas, and they had a 911 on the rack stripping it down with those wheels. They had more sets also. Its best to call them and ask for David. They can be a little price happy though
! Hope this helps.
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1970 T1 W/MassIVe 2913cc RAT/?EFI? w/direct fire (very soon) and 915 trans
1962 SC 1776cc SP 944NA brakes, 993 wheels
VKG