Since I have in my possession both a '97 and a 2000 head and valve covers I can say for sure the 2nd and 3rd gens are not interchangeable.
2nd gen 1997


1997 2nd gen

and here's the 2000 3rd gen


2000 3rd gen

Note the different bolt locations and that there are no extra (unused) bolt mounting bosses in the heads.

 

Actually, these two pictures show it better.


2000 3rd gen

1997 2nd gen

 

For reference here's the aluminum one


Aluminum

 

Thank you, sir