1997 - 1999 is pre facelift. 3.3l, Steel bumpers with plastic valence and glass headlights.
1999.5 is nissan using the leftoverparts, per facelift engine, post facelift body. 3.3l, plastic bumpers, composite headlights.
2000-2004 is known as facelift. 3.5l, plastic bumpers, composite headlights. Etc.