Mercon LV is listed as not being backward compatible for transmissions and transfer cases requiring Mercon or Mercon V. The same goes for Mercon ULV. Unless the manual calls for it for your transmission or transfer case, I would stick with the older specification. That may require going aftermarket.
As a side note, I have noticed that actual Mercon V shifts better in my manual transmission that calls for it rather than aftermarket product that says it meets the same specification. It works, just not as well.
Rock Auto sells actual Motorcraft Mercon branded fluid products, that might be a place to check outside of a dealer. No guarantees they have plain old Mercon but worth a try. Even with shipping, they are cheaper than the dealer.