Iron Duke, SD4, 4-2-1 header for sale. (Page 1/1) FieroWannaBe DEC 12, 05:53 PM I have the header from my SD4 engine, and I will not be reusing it, It should fit all factory Iron Duke heads as well, and was on my 84 SE with factory exhaust. It is a 4-2-1 style header. The paint/coating has completely rusted/burned off, but the header has not rusted through, it is surface rust from sitting for a very long time, I would recommend recoating it before use, I will include the old gasket as well. I can take more pictures. The primary diameter is 1-1/2" ID, 1-5/8OD , about 12" long into a 1-7/8 ID, 2" OD secondary, about 16" long, and a 2 1/4 Collector, with a test pipe welded in place of the factory Catalytic Converter. I am asking $300 plus shipping or pickup.