Mine was threaded. (M8x1.25mm) It must not have been to hard to remove...as I remember taking it off, but not HOW I did it.
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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