Nice bass! Oddly, the MJ serial number makes it, technically, a Mark King Signature Standard. A deluxe would have an MK serial number. I am guessing that it's because it has walnut top and back rather than cocobolo, since every other feature seems to match the description of the deluxe model.
Purely semantics, though. In terms of value, I can't believe this would differ in any way if it from a bass with an MK number on it. Good luck finding a fair trade for the bass you want. Consider offering this one for straight sale for the right dollar amount so that you can then track down and buy a short scale when one pops up. It will open up your market and could lead to a faster resolution.
-bob