Carpet install question

I am installing carpet in my 70 Duster and wondering should I glue it? The install instructions say to. I am wanting to replace the floor pans if I find someone to do it. So if I glue the carpet down this will cause issues for the body guy. I thought this carpet was was made to fit. [Not exactly] What is the best way to install it? Start from the center? The back? Side? Confused. How do I know when its tight enough? Any tricks? Thanks Tod