Over the years and as lately as a year ago, I have been installing bird glass in many 1968 cars that never came with it...I see bird glass for sale real cheap and i buy it just in case I want to install it in other cars I might own...In fact one of the 68's I bought recently had bird glass in the car as the previous owner was going to do the same swap....Has anyone tried to find out how many "bird glass" cars have factory tinted glass as well ?