The main problem stems from trying to fit CHEAP headers in an A body Chassis.
When I went from a 318 to a 440 in my Charger, my first set of headers were Hooker #5903. The car had never been in a wreck and I used new mounts. The headers still made contact at the LH torsion bar and the idler arm. I later went with Hooker #5209 pipes. Those had a 3&1 design with a separate pipe from the 4. Yeah, still a few points of contact. These TTIs clear everything, even the Fast ratio Idler and Pitman even though their instructions clearly state that they DO NOT clear.
I like the habit of UNDER promising and OVER delivering.