There are just keyhole shaped slots at the top on either side that the hook on the end of the tailgate chains go into. The holes are evident on both the gate and the bed sides. With my truck in the past it was the slightly bent tailgate that held it tight. In addition, a tailgate rattling was the least of my worries, I was more afraid the whole bed would fall off. Once I am done with current restoration, I may have to revisit this. Although, there is one distinctive sound all these stock trucks made, that is the sound of the tailgate chains slapping against the box as you move around.
Steve O