Don't know how the newer units are configured...our 78 has an interior panel down the center of the ceiling that's removable, with some effort, by removing several pop rivets to get to the wiring overhead.
I removed the original TV antenna in order to install a new Trav'let Sat antenna system. I had to 'fish' two coax cables and one control cable down forward to the old outlet box...I didn't want to deal with having to take the foward domed, plastic interior lining loose.
I used the original flat type TV antenna lead to 'pull' the new cables. I carefully attached the new cables to the old lead in a tapered sort of connection so there wasn't one big bulge. I also used a small piece of braided wire cable along the cable for add'l strength, and of course would electricians tape over the connections. I also coated the outside of the completed tape with some liquid detergent to help it slide....
It worked just fine, and the three cables slid through any existing clamps without any problems...it was a good sight to see my taped connection come into sight...