Well a long (or short) story

Went for run today and got 2 miles before coolant check light came on (so much for the planned classic car run with the HRCR)

Found leak is a pin ***** on the rear side of the expansion tank facing the wing (suspect that this is internal rust pushing out as the external surface of the tank is perfect - one of the checks I did when buying the car)

Can order one, but confused by part numbers

CAC8614 - supposedly from the earlier HE, but jaguar classic car parts site says it is suitable for my vin (an early 1991)

The CAC8614 Expansion tank and probe is available from Jaguar Classic Parts in the United Kingdom. Part suitable for use in XJS from (V)139052 to (V)179736 models.

CCC6725 - this is for the later HE and would be suitable (according to site) for my VIN

Part (CCC6725) suitable for use in XJS from (V)139052 to (V)179736, XJS from (V)179737 to (V)226645 models.

Question I have is what is the difference between these two parts? Anyone know?

Huw