genuine are forged aluminum and replicas are cast as you have stated.
og fuchs should have part numbers:
Info on Fuchs wheels, from the Rennlist website:
size - weight (lbs) - wheel number
5.5x14 - ? - 911.361.016.10
4.5x15 - ? - 901.361.012.01
5.5x15 - ? - 901.361.012.04
6x15 - 12.5 - 901.361.012.06 / 911.361.020.10
6x15 - 11.6 - 901.361.012.03
7x15 - 12 - 911.361.020.41
7x15 - 12 - 901.361.012.05 (911R wheel)
8x15 - 14 - 911.361.020.42 / 911.361.020.12
9x15 - ? - 911.361.020.03 / 911.361.020.06
6x16 - 17 - 911.361.020.43 / 911.362.113.00
7x16 - 18 - (911) 122 911.362.115.00 / 911.361.020.44
7x16 - ? - (944) 112 951.362.115.00
8x16 - 19 - (911) 112 911.362.117.00 / 911.361.020.45
8x16 - ? - (944) 135 951.362.117.00
4-bolt Fuchs 2.0Ltr 914 is 914.361.011.01 forged aluminum alloy wheel, weighing about 13 lbs .
hope that helps mate.
nick