The headers from Coast are 1-3/4", 16 gauge mild steel, 3" collectors. He can flange them for whatever heads you have. My mild steel ones were something like $635 to my door and he said he could do step headers for $100 more, and stainless for around $850 (ouch). He could do 1-3/4", 1-7/8", 2", 2-1/8", or about anything you want. This was a few years back.....don't know if he still makes them or not. Worth a shot calling.
JDM's Kooks longtubes reeeeaaaaally look nice, too.