The top grill in the front bumper is part of the bumper. When peeps revise the front end with a face lift (original front end changed to late version) they swap the whole bumper over. It's a direct fit, but some have found a small amount of plastic may need chopped oft on the inner side, by the radiator.
If you compare the top grill size, the later version is wider than the original. It would need considerable care to cut out a later grill from a late bumper and cut it smaller to fit in the original bumper. To the extent it's would be easier and neater to just change the whole bumper. The grill would need substantial support to keep it in place. There's a lot of wind blowing against it when yer at speed.
Video's on youtube of how to get the bumper oft. Go easy on it and disconnect the electrics as you go. Lower the bumper onto a blanket or card so you don't scratch it.