Others will tell you to search...but....
Not all were nikasil after a certain production point. If yours hasn't been replaced, it probably is nikasil by it's age I'd guess.
You can tell by looking on the engine block above the starter.
It's pretty hard to do with the car on the ground,
But there are different numbers on the block that denote if it is nikasil or alusil.
* 1 725 970 - Nikasil
* 1 741 212 - Nikasil
* 1 745 871 - Alusil
Sometimes dealers will spend the time to find out if the engine was replaced, but it depends on the dealer. And that might only work at the dealer it was serviced at.
Those numbers are for the 3.0 M60, not 4.0
There are ways to tell the condition of the nikasil you are looking at, searching will bring up plenty of threads.