I thought the S250 and S780 were the same box, but with a different bottom/wheel well. The S250 extending the full length and the S780 having a boxed in one, more interior space.
I'll have to do more research, because my s-780 Geithner box measures 84 1/2" wide, 102 1/2" long and 68" high (plus 2" rubber pad). It has lifting eyes on the top four corners that stick out 2" and on mine, there is a removable air conditioner support that sticks out 26" on the front.
Here is a photo of the shelter I have and the trailer it's being mounted on. I'll check back to let you know if I have to eat crow about them being the same.
At 102" wide if loaded sideways, the box alone would be at the legal maximum. I thought about doing that like a sleeper on a tractor...but too wide.