I've owned 3 different headers....
I had a Hedman header on my old red Zuk, it lasted a year or so before it fell apart. It also leaked from the center of the 4 tubes from day one.
We had a Calmini header on our black Zuk, it blew collector gaskets every couple months due to thin flanges that would heat warp. It sat in our driveway in the junkpile for years, finally gave it to a customer.... who now regularly blows gaskets. We actually sell quite a few of our reusable aluminum gaskets to owners of the Calmini header.
We've had a Thorley header that's gone thru 3 Suzukis, got it in about 95', its still going strong (sold it since we're running TD's now). Quality matters.
Pay a little more now, or pay alot more down the road....
On a side note, the best power gains were from the Thorley header too. Even though the one is a copy-cat of the Thorley, the Thorley uses larger tubing and better fitment to the manifold for a freer-flowing exhaust.