I wonder if the telescoping antenna only came with the AM/FM radio option. You don't need an adjustable mast for a single band radio.
From my past readings from alaska T/A was that the telescoping antenna's were used on A/M radio's.
The fixed mast were on AM/FM radios.
Wade Ogle had his restored Red 71 Hemi cuda vert at the show this week-end.
It had a AM/FM with a telescoping. So now I can't be sure.