yep, recall that thread and that they were no longer available. not sure that size is correct, it's definitely doesn't seem to be a fine thread. the coarse stuff I had laying around didn't really work either (nor did the fine) - only the original acorns from some other mirrors I had would "kinda" go on there. Really odd that the extensions would have a different size stud (but they were integral to the extension also, and original - and I had boxes o nuts that fit the extensions). But the stud is integral to the mirror arm, so it is original also. The plot thickens, but they are on there solidly now. But, I may at least pick up one that I know is 3/8-20 and see how it seems to fit - my recollection was that it was a no go because of the very low thread count of the studs.
Not 50 mph yet (winds), but supposed to be coming this evening and in the 40-50 mph range til at least monday night. normal ops around here. the cap is already listed on the pennysaver!
http://www.pennysaverusa.com/classif...-67166349.html and the parts board
http://67-72chevytrucks.com/vboard/s...d.php?t=575660. The 71 cheyenne super may not be far behind it..