Ed, here are stainless headers on ebay:
http://www.ebay.com/bhp/chevy-350-stainless-headersIt's astonishing how inexpensive they are. Over the years I've contemplating making stainless headers for my '32 Ford roadster street rod so I've looked at the prices of stainless steel tubing and U-bends. Just the materials to make a set of headers would have a retail price of about twice what these complete headers cost. It makes me wonder what stainless alloy* they are made of, the thickness of the tubing, the quality of the welds and the flange fitment. If those issues all check out favorably they look like a really good way to go.
Stainless steel does yellow slightly from exhaust heat and the weld areas get that same yellowing during fabrication. If the weld area is overheated it varying shades of blue, not yellow.
* I'm told that not all stainless is really rustproof and 304 is the best alloy for exhaust use.