will a 3.8L engine from a 99 grand prix fit in a 2000 Bonneville??

All 1995-2005 L36 Series 2 engines will fit all platforms originating a Series 2. Only thing to remember is to swap over all sensors/brackets if there is a year change.

All 1996-2005 L67 Series 2 engines will fit all platforms originating a Series 2. Only thing to remember is to swap over all sensors/brackets if there is a year change.