Correct, the passenger side is the antenna cable port. The driver side on my Mach has this factory installed rubber plug.
Don't know for sure. Good question though.
I got the same rubber plug set and it did have the correct plugs for those two holes in it.
When one of our cars had power windows or speakers from the factory there is an extra, larger hole drilled in the pillar. The rubber conduit that the wires for these accessories go through fits in that hole. If the car was not equipped with either option, the hole is not drilled but there is a small dimple in the metal, on the pillar and the door, showing where the holes should be drilled. My car did not have PW or speakers originally and I wanted to add speakers, so I a bought the conduits and drilled the holes in the pillars and doors for them. I don't have a really good before pic, but the last pic shows the dimple before I drilled out the pillar I circled it in blue.
