I'm trying to get a water pump for my 1993 400E. There seems to be 2 different part numbers...one for m119.975 020771 (water pump part no. 119 200 15 01) and one for m119.975 020772 (water pump part no. 119 200 21 01)

how do I find whether I have 020771 or 020772 engine? I hate starting threads, but I can't find anything on this...

Thanks