I have a 78 with CB option. Of course the antenna is defective so I bought the GM replacement GM# 12355706. This antenna will need some engineering to work. The antenna cable from the car is too big for the jack on the new antenna. The antenna came with a new splitter. I pulled the carpet back to reveal the original splitter and found the cables to be permanent mount. That is no unscrewing to remove. The new cables will not go all the way to the radio unit so now what am I to do. I hope someone has an answer to my problem. Thanks Rodney