thanks for all answers, but dougs headers technical support wrote like this to me when i ask this question
answer:Sorry we don’t offer header for the 74 darts. The 72’s have a different chassis then the 74’s. Slight change but enough the headers will not fit.
I have flaming river 16:1 steering box in my 74 swinger but i don't believe that's a big problem. 67-72 and 73-76 darts, whats the difference between chassis, is that older body wider (frame rails) or what?Maybe i try those dougs headers... or maybe i purchase tti:s