Can you put a front end o f 1999 Camaro on 1996 firebird?

No, you can't directly put a 1999 Camaro front end on a 1996 Firebird. While they share some platform similarities (the F-body platform), the body structures, particularly the front clip, are significantly different enough to make it a highly impractical and near impossible swap. The fenders, hood, headlights, grille, and bumper are all unique shapes and mounting points. You'd be facing extensive fabrication work, likely requiring custom modifications to the core structure of the Firebird.