2nd Gen Headers!!
http://www.schoenfeldheaders.com/ford_street_stock.htm
I called and asked whether this header would fit a stock clip, and explained that I intended to cut off the Ford flanges and weld them to an LS1 flange. The tech agreed that this should work, and offered to build them with LS1 flanges in the first place - he says they have built their SBF headers with LS1 flanges "quite a few times". I ordered them up - $209 plus shipping. When they arrive, I'll take some measurements and let you know how they look. For this price, I'm not expecting miracles in quality, but it's hugely cheaper than custom, they have 1-3/4 inch primaries, and they look pretty close to equal length.
I will bolt them up when they get here, take some pics on the engine stand, and make some key measurements at the usual interference points. I'll also leak test them somehow.






