The factory rear 61 & 62 rear antennas are the same, assuming it’s a original rear antenna.
screw the top chrome and plastic cap at the base of the antenna mast will screw off to start the removal.
under the chrome & plastic cap is a 3/4” hex nut - remove that nut.
Then the chrome mount that sits on the rubber gasket on top of the rear 1/4 has one small hex nut on a stud on the bottom side of the rear 1/4 sheetmetal. Remove that hex nut ( the stud may come out with the nut ) - after that small nut is removed the antenna base inside the trunk will drop down into the inside of the trunk with the mast attached.
All factory 61 & 62 rear antennas have a L shaped bracket that holds the base of the antenna to the rear wheel well.
this bracket has to be removed and should be reused on the new 62 to stabilize the antenna. Reproduction rear antennas do not have the same base or mount to stabile the antenna.
The mast on the antenna can be pushed down or up inside the section of the antenna in the trunk.
The mast has a 3 sided base that the 3 section factory mast must be pushed into for a correct fit .
Paul