Engine knocking

[JBROYLES000]

I HAVE A 2002 WRX WITH 57,000 MILES. THE ENGINE STARTED KNOOCKING AND I CAN’T TELL WHERE IT’S FROM. I EVEN CHECKED WITH A STETHASCOPE PROBE.IT’S LOUD. ANY IDEAS BEFORE I PULL THE ENGINE? ANY PLACE I COULD GET A USED LONG BLOCK? THANKS