tti exhaust on doug headers

i have a 3 inch tti exhaust x pipe system and im putting it onto my doug headers.. for a 72 demon with 408 stroker.. need tips on how to set this up.. do i need to get the header adapter kit? cause i cant get them to meet up properly.
What parts do u have now. You need the x-pipe ....two elbows and two header adaptors/reducers