Pretty sure the tubing I used is steel. That is what the seller said and it felt like steel. I'll check it with a magnet. It might be thinner than factory, so bends easier. It is coated, a dull silver outside and looks a bit gold inside. I forgot this was a slant forum and I did this on my 273. The slant is the same up to the middle of the engine, then the tubes snake up over the driver's engine mount, at least they do in my 1964 (those tubes are fine).