The Units package includes various units that are called ton/metric ton/tonne/short tons but not long tons (LT). A long ton is equal to 2240 pounds of weight and is part of the imperial system, so it is also know as the "imperial ton" or the "weight ton".
This unit (the long ton) is used extensively in naval architecture and ocean engineering. I would hope that you consider adding it into the next update of the Units package.
Or perhaps, it would be nice if one could make their own user-defined units. So if this were possible i could create and save a new unit (the long ton) by defining it from previous known units (2240 lb).