tailgate metal layers sperading what can be done to fix?

[67chevy1series]

me and jasonbird have both talked about our projects through pms and both have a common issue in our 67 tailgates the 2 layers are spreading. what can be done to fix that jason's and mine are in good condition and are original to the cab or truck so it would suck to have to throw them away so what can be done to fix this?

any ohthers that have this problem go ahed and ask any questions that may have not been asked on this matter...

thanks for soon to be help!