You might have a tough time finding a road widener that will handle a 6 foot spread. Maybe even look at having a paving contractor run it through a paver. They can drag along over an area like that with ease. Though the paving contractor may not want to run straight rock through their paver.....but you never know.
I think using the skidsteer bucket would be pretty time consuming to run 6000 tons through.
I really like the redi mix truck idea. Like it was mentioned, truck the rock to a redi mix plant and have them load it and short haul it to the job.