I have been informed that the black plastic hold down nut is not correct. The skylark one is shorter. The Antenna and base is correct 1966 skylark. I have seen the shorter nuts for sale on Ebay. Thanks.
buick farm has the shorter nut for 28 shipped buick farm also has NOS masts for 59 shipped hence my offer of $100 shipped for this used assembly with an incorrect hold down nut