650 C sounds plenty hot enough for engine, but not 100% on downpipes, although I shouldn't think they'll get THAT hot....
I suggest you contact these guys: http://www.paints4trade.com/index.asp
I've used them for some projects at work - very helpful & should be able to recommend the correct product. Not sure on engine colour, but if nobody else has the correct RAL colour code number, I have a chart at work which I could fish out next week......