I am going to look at a 4-speed next weekend and the guy can´t tell me for sure what it is. The casing is made of aluminum he thinks.
Cast on the passenger side: 1304065903 W.G.DIV FPC2 (with the P lower than the rest) 1/8/1975
Cast on the driver side: B.W.13.04.066.901
Stamped on the driver side: WB2552
Cast on the cover: 13-04-097-90# and under that G297#
Anders