I have the TTI's installed in my 360-395 '65 Dart w/Keisler 5-speed. Any header you install in these cars will require lots of work. This is best done on a lift with a helper. However, they do fit just as TTI promises with NO modifications to frame/chassis. You can get their install instructions by writing them. They will ACCURATELY describe the install procedure. TTI's are expensive but of the highest quality and workmanship. YOU GET WHAT YOU PAY FOR.