Don't know if a '79 is the same nut on an '87 there is a rubber plug/grommet in a hole just above the floor pan down behind the driver seat.
Thats where I ran the Innovate LC-1 and MSD 8762 wires into my car, and then on up along the edge of the center tunnel under the the seats and under the carpet.
Here's pic of it with a red arrow pointing at it.
