Radio antenna

Some, like my 67 B'cuda, have a telescoping antenna that doesn't fully retract.
The solid mast that screws into the base is more common/standard.
The antenna base along with the hole in the fender did change at some year model but I don't know exactly when. If I was going to buy a OEM antenna without research, I would look for 68 or 9 with fingers crossed.
The very best solution for a car cover is antenna delete plug for fender. Route a long antenna cable down the right inside and toss any little part yard antenna in the trunk. It works for todays more powerful local radio signals, even better in a tent/vert.
The problem is finding that delete plug. They are rare as hens teeth.