I just moved a stump with a 10 foot section of the tree on it that fell on a neighbor's driveway..
I could not lift it with my tractor, but I was able to lever it.
Dugg a little trench under the nose, put some small logs under it and then built that into a lever. used the loader to push down on the lever( a small steel beam).. Got it up high enough to put several large (roller logs under it).
then drug it about 100 feet.
I suspect it was about 1200-1500 lbs..
Now as far as for the trailer...
If you can get your hands on some 3-4 in galvanized pipes at least 1 or 2 foot longer then the trailer is wide, these could be a good way to drag it..
It would likely take at least 8 to 10....
so the process would look like this:
Lever lift the box, put some under the front. and some in front of the trailer.
Pull it forward, and have at least 2 people to move the pipes as you slowly pull it... When the pipes get to the back of the trailer, have them moved back up front....
It has been at least 20 years since I saw this done, and it was done for a ~15 by 20 wood building loaded with tools... So weight should be about the same... I seem to recall this was done with an old Ford tractor- no idea the model or HP.. But it was not much bigger than my
L3400 if I remember correctly.....
And it was on flat level ground. grass was cut and all was dry...
We also used to do this in shop class in high school with empty storage buildings (8x10 and 8x16) and we used 4 in PVC for them.. Built them in the shop, and rolled them outside after building them.
I hope this helps...
J