Not sure if this is unique to the 66 or not. But I think the boot I got with the convert last fall is missing something. Looks like there should be something that slides into a metal rail on the top of the back seat. And that it should have some way to attach it to a valcro strip that is sowed into the front of the boot. I contacted the guy who I got the car from. Maybe he still has it or his friend that he got the car from. I suppose something could be made. Thanks
Well I found some information. There is a Velcro Strip that slides into that metal slide strip. And Ames Performance has a repo one for a 66 GTO. It should fit or can be made to fit.