There is some over-broad info above. The ring and pinion ratios vary in 1969. I finally got a 1969 factory service release and sent it to the folks at the 912 registry, and they put it in their table at :
912 Registry | Transmission Type Table
Take a look there. In 1969 the factory changed from aluminum transmissions (902/04 and 905/05) to magnesium (902/06). I don't remember what the 902/16 or 902/55 cases are, but there are many kinds of 1969 transmission, so be careful!