Bulldozer
free ice cream sandwiches
Mine were side window louvers too. I didn't have any dimensions, just laid a sheet of plastic over a spare window, shaped it with a heat gun and then used that as the frame.
Cut it out and shaped each slat with the heat gun, plastic welded them on and sanded it down. Didn't have any money in the materials, since it was stuff I had laying around the shop anyway.
On mine, the slats continued to the end of the window (With a tab underneath to bolt on to the window/hinge)
I might try making another set again.
this is what im working with. they fit much closer than one might think. im going to cut and fab them to fit my side windows . these are plastic so it shouldnt be too hard
heres a photochop of what i am after at the bottom