Dave they are the S400Sx's. He will know the complete line just off that naming system. Direct part # is 177101 for that particular unit. We keep them in stock with our Turbodiesels.net shop.
They are an awesome piece indeed. Very nice stuff, and they also make a 60psi and 120psi model as well. Though I doubt anyone here will need that much boost. :D
Turbosmart East is a stocking wholesaler. Also turbosmartonline.com as well.
Sick pictures.....that 98X is working well for him. He's making over 1000rwhp at only 20psi and a small 366 LS1 motor. It will be fun to watch when he's in the 30psi range.