Classic/Antique Car Repair: reinstalling 1968 mustang radio antenna, antenna base, removeable panel

Question
Any guidance on how to reinstall an antenna on the passenger side front fender of a 1968 mustang coupe?  I just had it repainted, and when I got it back the antenna which was loose dislodged from the hole in the top of the front fender.  If it has to be screwed on from below the fender, how does one get underneath that fender to secure the antenna.  This is for a round based antenna. I noticed the precut hole in the fender has a very small cutout on the circumference which suggests that you would insert the antenna base from the top and just align and then twist and lock it into place.  I just see no way to access the area below the hole in the fender to srcew on from below a retaining nut.  If it is something I can do very simply, I would prefer not to return it all the way to the body shop.... I can't believe that you would have to remove the entire fender for access to install the antenna.

Answer
There should be a removeable panel that shrouds the wheel - you may have to remove the wheel to get at the fasteners to take it off.  If the panel has been welded on, you will have to have long enough arms to reach up from under the car - there is an opening there, but it is a loooong way up there - get your neighborhood 7 foot guy to help you - he will have long enough arms!  I'm sorry, there is no easy way!

Dick