Here ya go. The piece you need is on the lower right. You'll need the screen also to keep rocks and small dogs out.
They're made of sheet metal and take a beating over the years. I think I remember where it is in my garage. If not it may take me a couple of days to locate. I know I don't have the screen.
In the mean time you might post a wanted ad in the classified section?
Thanks so much for the info. If you have one, that would be even better. Anything else you want to get rid of I may be able to use on my 55 Customline ?