Tom, leaving the glass out forever is easier- just reinstall the chrome frames once and for all. From 20 ft away, it just looks like you have exceptionally clean windows! My side glass has been resting comfortably on a garage shelf since the last century. It also removes 10 or so lbs of unneeded weight.
Along the sides of a Pantera, the airflow boundary layer is about 2" thick, so there is no aerodynamic drag penalty for no windows. The Maserati Merak also found this out. Matter of fact, airflow direction at the rear quarter window area is outward from the engine compartment, which is why those small side airscoops don't do anything until you get up around 160 mph when the boundary layer thins out. The much larger 'elephant-ear' scoops protrude out past the boundary layer and do gather some air (and drag).
I once asked Tom Tjaarda about the cast louvers just in front of the windows, and he said they were supposed to be open like on the Miura, but on the Pantera prototype they found out that no air went in thru them, so Ford/DeTomaso made them as a styling thing, and saved a few bucks. Tom said he still liked them.