<<<1/ Use a donor westy evaporator shelf/fan (blows from the rear)
2/ Remove the center duct from your existing unit and allow air to blow
from the rear (actually cools the front better than the westy unit in my
opinion)
3/ Install the center duct with quick releases (perhaps something like
the air cleaner over-center wire clamps, but think beefier) and remove
the center duct when raising the top>>>

Or, scrap  1,2, & 3 idea above , sell what he has, and buy a Westy with
AC.

Wow, what an idea!

Oh Boy, quick release clamps on the ductwork.
I smell a Rube set up in the making.--: )