Here's what I have in my '56 3100, they're black D rings so they match the floor. I have 3 down each side and 2 across the front for a total of 8. Keeps all my stuff where it belongs with the 1" ratchet straps...
For security you could add a bicycle chain lock that's covered in plastic through the D ring and around the cooler handle...would be enough to keep the honest person honest.
Mike B
