Dwarf Longbeards Question

[Trains_Get_Robbed]

Currently building a doubles list for a friend and I when I stumbled across the rules for Longbeards in his book.

They are sweet with the stats boost and all, problem lies under their conditions however: you cannot have more units of Dwarf Warriors than Longbeards -unless you have a King .

This being said, later in the book you are allowed to upgrade a unit to being Rangers for again, additional points. My questions is this:

If I take a unit of Longbeards and upgrade them to Rangers are they still considered Longbeards?

Are Rangers they're own separate entity, thus essentially allowing one to "bypass" the Dwarf Warrior unit restrictions that are normally placed on Longbeards? Or instead do the Rangers (or in this case Longbeard-Rangers/Warrior-Rangers) keep their classification of Longbeards, while being Rangers? If so, then isn't this semi-contradictory to the classification of Warriors? Longbeards essentially aren't REALLY Longbeards, but like Rangers with a surname attached to them ie; Longbeard Warriors.

Otherwise this would be a unit entry mess.