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.