On each door there is a rubber piece that attatches to the door and contacts the window on the outside as it goes up and down I guess to keep water from going into the door. What is that called and where can I get a pair?  It looks like it is attached with little rubber clips. How can it be changed, ie does the window have to come out of the door? Thanks a lot, folks for any info you might have. My other rubber gaskets are in really good shape.

Convertible Top Specialists have them also.  I need to get a set myself.
http://www.topsdown.com/1971-1980-Ford-Pinto-window-sweep-set--p1023.html
I did get their door weatherstrip and window channels and was happy with them. 

You MIGHT be able to pop the sweeps out with the window all the way down.  If not you will need to remove the door panel and lower the window-down-stop so you can lower the window another inch or so.  That should give you all the clearance you need.