The H8000FW is different from other Eventide equipment in that it has no internal WC (Word Clock) termination, allowing to be used in the middle of a WC chain.
This does mean that if it is to be used at the end of a WC chain or cable it requires external termination. See the User Manual for more information.
If external termination is used it may be 50 ohm or 75 ohm (the H8000FW does not care), but it should match the source.
Or, to answer your question directly, 75 ohm will be fine.