You can follow this tutorial and adjust the width if needed - https://www.charlestoncrafted.com/how-to-build-a-rustic-barn-door/
Hi! Here is a link on how to build a wide barn sliding door!
This may help: https://www.hometalk.com/14808132/30-easy-sliding-barn-door-hardware
You'd just have to fix the dimensions for what you need for your custom project.
Here are some by other Hometalkers. Just adjust the dimensions for your opening.
Here is how we built one, just change the measurements to fit your space: https://thehoneycombhome.com/how-to-build-a-sliding-barn-door-for-less/
Make sure your door hardware is rated for the weight of your extra large barn doors otherwise you might run into problems.
Not only the hardware, but the framing in the wall needs to be able hold this load.
There are lots of sliding barn door ideas here:
This article may give you an idea of how to build them: https://do-daddy.com/how-to-build-diy-double-sliding-barn-doors/
Hope this Helps! Jeremy - https://do-daddy.com