Another window question from yours truly... :<)

I was contemplating swapping the vented rear side windows on my '90 parts van
to one of my earlier vans. Can they be be added into the '87 down vans?  Is
the fresh air recirculation vent totally self contained in the plastic vent
that you can see from the outside, or is there parts that extend down into
the body surrounding the window?

I'm assuming this will increase fresh air circulation within the van by
drawing air thru all the way to the back, rather than just bringing it in
thru the dash and spitting it out at the rear corner of the front doors like
on the '87 down vans. 

Anyone done this?

chris