I used caulking cord. It comes in a roll about 1" wide that can easily be "torn" into 1/4" strips. Has the consistency of putty. It is available at any hardware or home building center in the weather strip dept. Just keep it slighty warm to make it easy to use.

Those little things were mounted on the outer ends of the header panel and a 4" turn signal screwed into the end. I know they were used on the 64's and some of the heavier slicks. They were required in some states ie: Pa at least. The grill lights then used 1 wire and were for parking only.

I believe you box is the old style because it is 4 wheel drive.