Pictured here in this photo gallery are the smaller fan housings and fans used in by the 1973/1974 Porsche 911 RSR (the 906 also used a small Magnesium fan but I don't have the casting number. Porsche may have also used this housing and fan in other race engines). I am not sure if the 901.106.103.00 I was given is the actual Porsche 'part number' or the 'casting number' and I will have to verify. Here is an RSR engine and with the small 226mm Magnesium housing https://pbase.com/slidevalve911rsr/image/65758711
The casting number shown in this reproduction is 901.106.101.0R https://pbase.com/slidevalve911rsr/image/64312716
:: 226mm Small Fan - Factory Original Magnesium ::
:: 226mm Small Fan Housing Reproduction - Germany ::
:: 226mm Small Fan Housing Reproduction - France ::
:: 245mm Fan Housing, Magnesium - Not 906 or RSR ::