Digital BW, The Print

I inherited an Epson 7600 that has been using the UT7
ink set.  I want to change it over to use the MIS
Eboni-6 inks, and asked here for some advice on how to
clean out the old inks in preparation for the
changeover.  By the way, thank you for the replies.

Anyway, upon telling this to the previous owner he
asked "why bother?"  He says that except for the ink
in the PK slot, the UT7 and Eboni-6 ink sets are
identical.  

Now I'm confused.  Is this true?  If so, can I top up
cartridges partly filled with UT7 ink with the new
Eboni-6 equivalent without any flushing or cleaning?

Thanks in advance!

Ken