I purchased a rear window glass from LMC for my 74 c10. They had two options for windows, one for a 73-75 and 76-87. So I bought the window and rubber for my year. I tried and tried to get it to install but it seemed too the window was too big and would not fully seat in the truck. Am I missing something obvious here? I thought all the window sizes were the same. So why sell windows for different years? Any help or ideas would be appreciated. Thanks!