I recently acquired a 1986 K75C for parts and it included a good running fuel pump which i want to keep as a spare. Looking for best way to store it for later use.

Thoughts?

If it is as old as the bike which is quite probable then the rubber sealing ring around the top will dry out and crack then when you do go to use it fuel squirts out the top around the crimping and you don't get enough fuel pressure for the bike to run properly.
If you want to cary a pare get a cheap new one and you'll have one that will work when needed.

I flushed mine with LPS 1 contact cleaner followed by spraying in copious PTFE lube and then stored it in a sealed plastic bag. It's been stored in the tail for nearly twelve months. The problems I have also seen with used pumps is that unless flushed they can rust internally. Will it work when I need it, I am hopeful. Eventually seeing as the Chinese pump that I fitted as an experiment is still going strong I'll buy another in twelve months time. 
Regards Martin.