I have a 68 GTO. had to replace the trunk gasket and found that it did not seal well using the paper to test. The 68 has a fragile lip that the gasket fits in and can get bent from putting something heavy in the trunk either from the back or the sides. Use a 6 inch long 2x4 and a reasonably heavy hammer, place the 2x4 vertically under the lip where it is sagging and tap gently with the hammer to raise the lip and test again. Do not hit it with the hammer as it will get a dimple and it will be hard to get out, the 2x4 spreads to load nicely if you're careful. It can be a tedious and time-consuming process, be gentle and test often and you can make it seal. I had my GTO in a Florida Monsoon rain without any leaks.