Have an 80 Z28, want to install some louvers that I found at a yard sale. The mounting brackets are totally missing. Any idea where I can find them?

 

That hardware is likely to be proprietary (exclusive to that make), so you might want to find out what brand the louver is and do a search from there or contact the company.
But considering the final product, I'd say using duct tape would be an appropriate attachment.
And don't forget to add fuzzy dice to your rear view mirror.
Can you tell I don't care for louvers?