A metal adapter wouldn't be the only option available to you. When I fitted a non-standard topper to the bed on my 04 Ram 1500, I used pressure lumber to make a framework that slipped into the stake pockets and attached the topper to the wood. When painted the same color as the black bed liner, the adapter virtually disappeared.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!