You may want to remove the rear seat to get the package tray off the rear - the front seats won't really get in the way.
I don't see how you can do it without removing the glass like Andrew said earlier.
I always use a piece of wire and tighten the front bow to a hole in the windshield frame to pull everything tight. ( I will see if I have pics to show you)
The rear pillars are the hard part to get right - just pull for a while, and when you get frustrated, walk away for a while.
I installed the headliner on my '66 coupe in the winter using a heat gun - $9.99 at harbor freight.
Check out this article -
1966 Ford Mustang Hardtop Headliner Install - Project Build - Mustang Monthly Magazine
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Beri Fraley
Strong, Proud and Ugly
If you find yourself in a fair fight, you haven't been trained properly.