pedestal under the Air Conditioner?

[Pele2048]

There is a 2 inch or so tall pedestal under the air conditioner. (AFAIK, my air conditioning is original to my 2004 TM 3023.)

Should this pedestal be considered a part of the air conditioner and it gets replaced when I change the air conditioner?

Or should this pedestal be considered part of the TrailManor and stay on the trailer until death do they part?

Will any replacement air conditioner fit the opening or are there multiple sizes?

This influences how I'm going to be sealing up water leaks around the AC.