Not sure the situation but usually a shipping container is set down wherever you want it to be, and you start filling it with junk, pretty quickly going well past what the rated capacity of the M720 is. Not much point in having the container and not filling it.
With a little time and money you could probably build an adapter to use the M720 on the container as it's just a hooked bottom lip and a couple arms with bolts that connect it, and a simple tube steel frame going to the 4 corners on the end of the container, 2 uprights on the sides, a bar across the bottom with a lip added, and a second cross bar the height of the upper arms on the dolly with threaded holes for the bolts would be simple enough to fabricate if you have the tubing and a welder, but the steel these days would likely cost you as much as the dolly would.