TTI Header Help

I am looking for some advice on installing TTI headers on my 1973 Duster. I have read through threads looking for how others installed them but have just seen people say they just slipped in and were the easiest headers they ever installed. If anyone had them just slip in, what was in their car when installed?

What would you guys recommend having in or out of the car when installing the headers? I know people also say follow the directions, but I was wondering what people have experienced while installing the headers.

Thanks