If your friend built the K2 himself then he will know the history of the Elecraft K2 hardware and firmware versions of the various system and option modules.
This is required because the K60XV option is not comparable to a simple plug and play module, even if the K2 hardware and firmware is at the required level.
The K60XV option was primarily designed to integrate the Elecraft XV50/144/222/432 family of transverters into the K2 system.
Since these transverters have also been discontinued in the meantime, it is to be hoped that someone will offer the K60XV option for sale.
The only problem is that you can’t just unplug this module - if you want the K2 in question to continue to work…