Sliding door for pole barns

What's the best (strongest) way to install a sliding door on the end of a pole barn? My door will be 6' x 8'. What kind of header should I use on which to install the track? I can't use jack studs to support the header because my horizontal nailing studs prohibit that. Should my header be a double 12" x12"? Will lag screws be strong enough to support the weight of the door?

I would appreciate your advice.

You need what is called a 'CANNON BALL TRACK' found at a lumber yard that handles gates and farm supplies. The Cannon Ball system is the smoothest operating system you will find but there are other systems that will work well but check at a good lumber yard, not a box store. You get what you pay for.