I see a clock with the arrow in the 7 position and below is 5 C 20
The 3970010 block number is often associated with Chevrolet small-block V8 engines produced between the late 1960s and early 1970s. However, without specific additional details or context, it is difficult to determine the exact year or application of the engine. The "K03 25 TXE" code doesn't provide any recognizable information related to the year or application.
3w4n k03 p03h j3j3j3j3j3j3
The Turbo found in the 2001 Audi A4 Quattro is made by KKK and is the K03 version.
Stock turbo is a K03, If your looking to upgrade( raise the boost) I would got to a 306 forum and check out what other 306 owners have bought and what they recommend/like. You can also get a feed back as to positive/negative affects of the change and what they would have change/recommend changing.