Others may have better photos but here's how the sidesill carpet should look on your 79. The anchor bolt mounts with the carpet pulled back and a small slit in the carpet only for the belt to pass through. The plastic cover top sits on top of carpet when complete, rather than floating in the air when bolted straight through the carpet side.
Carpet and seatbelt1 by
Ben, on Flickr
Carpet and seatbelt2 by
Ben, on Flickr