I'm fairly certain the bolt pattern and centerbore is different on fan pulley hub vs water pump flange/hub, but I've certainly been wrong before and would actually like to be wrong here since it would make solving this problem easier for everyone involved.
I did look at two water pumps for and from my XJs. Yes, the hub is different. I did look on E-Bay. Maybe the 93-98 GC. ?? :
https://www.ebay.com/itm/2925206108...qmKdsEgmH8aCsXDbsGsSfwlQ==|tkp:Bk9SR_qVpNijYw