I came across this picture the other day
It shows Ivor Wynne in September of 1980 and they still had the 25 yard endzones, I can't remember the year they reduced them to 20 yards.
As well, it you look at the picture that's when they renovated the press boxes, the 2 spotter's boxes are gone and are in the process of being rebuilt.
Here's the web site that the picture came from: http://photogallery.thestar.com/photogallery/919736
They've got a couple other interesting pictures of the stadium over the years.