Kenwood TS-520S Owner's Manual
http://www.kg6haf.com/downloads/520S_manual.pdf

PAGE 25 -- Block Diagram for this transceiver.
NOTE Table 2 for MET Frequencies

PAGE 28 -- Schematic duagram of the RF Board (Figure 16)
NOTE that X44-1160-00 (Oscillator Coil Unit) is the Sub-assembly with these oscillator crystals (including AUX)

Kenwood TS-520S Service Manual
PAGE 16 of this manual shows the X-Ray of PC board and parts layout. NOTE: Crystal and Required Coil location.
http://www.kg6haf.com/downloads/520S_Service.pdf

WARC conversion or AUX usage, not really practical with 520/820 models -- that's why 530/830 exist !!