Like Bob said, you will have to ground the lights. The metal mounting holes are for the ground wires. My old lights were like that as pictured here:
Note the poor way of how the old ground wire was split and pressed between the old marker light rivet and the body. I removed all of these wires and rivets when I removed the lights. My new lights were like yours with 2 bulbs:
Since each bulb requires a ground, you will have to run a short wire between each socket set. I put mine inside the light assembly but you can also put the wire inside the body with the ground wire. Use Stainless Steel screws, washers, lock washers, and nuts (I used 8X32 1 inch long). It will make any future repairs a snap. Now crimp a connecting eye to the white grounding wire:
Hope this helps,
Terry