You do not need to replace the timing chain because there is no timing belt at all on Ford Taurus. It has a timing chain.
It has a timing chain that should last the life of the engine.
The 1999 Ford Taurus does not have a timing belt. It has a chain that requires no maintenance.
In a 1999 Ford Taurus : The 3.0 liter " Vulcan " V6 engine has ( 1 timing CHAIN ) The 3.0 " Duratec " has ( 1 timing chain to each cylinder head , so there are 2 timing CHAINS )
In a 1992 Ford Taurus , both the 3.0 and the 3.8 V6 engines have a timing CHAIN