I'm going to throw my vote for VEtte Doctors American Racing Brand Headers. ECS and 21st Century muscle cars sells all the brands being mentioned here in this thread...
Call the tuners and ask which one they like.
I tend to like to purchase the brand the tuner/installer prefers to use.
I like them to purchase the header system for me as well...
I like them to get as much profit as I can...for the people doing the work?
If they charge me the same price then what do I care?
I tend not to like to bring a box with me into a shop..
Thats a route I personally choose over the years..
Seems to work for me as I don't do most of the installations myself..
I do like the work they do to be easy and thats one of the reasons I choose the American Racing brand... that and I like the Merge collector as its supposed to be very good...and the price of under 1500 including high flow cats and X pipe is right on the money..
HTH and JMO..
I dont' think you can go wrong with LG's...or Kooks or American Racing Brand.. All very good..