Finally got the antenna in my '53- end of an 8 year resto. I cannot seem to locate the nut that goes atop the black plastic spacer and screws down on to the shaft. Can't recall what it looked like- a chrome dome, perhaps? Can't tell from pix of other people's what it should be- hard to search for something you don't know what is.. Currently using a brass hex nut which I imagine is not correct. Can someone enlighten?