I don't understand what changes you mean. You have to remove everything the instructions tells you and then reassemble when done. I had Dougs headers on my 65 small block Valiant back about 1997 or so. I like Dougs because they were the makers of the original D Dart headers in 1966 and know about these little cars. Plus, TTI, IMO are over priced and don't always fit right. The only "change" I am aware of is the little starter. Other than that, you simply follow the instructions. The Dougs will FIT the car. You might go to the Dougs web site. I am sure you can download their instructions and find more information.
Oh one more change......I believe you have to use the 90* oil filter adapter. I did on mine.
