I have a set of Doug Thorleys THY-152-c that I had to repaint they are 1 3/4 primaries 3" collectors. Work with Iron or Edelbrock heads had them sense 2006 on my 440 Barracuda. I am switching motors to a 500CID and just bought TTI's 2" collectors and 3.5 Primary. If you are running a mild a 440 the 1 3/4 do nicely. Not sure where you are at, but I am in Northern MD and was planning on selling mine at some point soon.