I am shipping my M816 from California (hopefully soon). I put down the measurements as:
32'L x 8'W x 10'H and weight at about 36,000lbs. These might be a little off but they would be high instead of low so you should be safe with them.
I think a M543A2 should be around the same size and weight.
tell them to get a drop deck or a RGN trailer, - removable goose neck so its easier to pull onto the trailer.