Mopar A body headers on a 73 d100?

I wish Hedman still made their Tork Step headers for D series pickups. I bought a set to put on my D350 with a 360. Hedman said they only fit a W150, but I tried them and they were some of the best fitting and working headers I've ever had. I bought them around 2003-2004ish.
Never heard of them. What was special about them? Now you’ve peaked my interest.