This is a brand new set of GT6 headers that have been High Temp Coated by Jet Hot ($275 cost alone). Never installed. Bought for a customer that ended up not using them on his car.
These do require modification to the frame to fit. This is a common thing with aftermarket Spit/GT6 headers, even the factory had to do it.
Instruction on what you need to do:
Mark the outline on the frame, leaving perhaps 1/4" clearance for the pipes. You want the smallest notch that will clear, so make the first cut on the small side, and then open it up as needed (much easier to trim away more than to put some back). The frame is just 0.093" mild steel, so a simple cutoff wheel will make short work of it. Once you have the cutout to clear, make up a filler piece out of similar thickness steel sheet, weld it in, trim and paint.
$550 through the forum, $599 on ebay.