While the bumper brackets do pass thru slots in the fenders, the bumper mounting area on the apron is different. I am more inclined to believe that the complete rear apron was changed and would be happy to bet that the front apron hasn't been left un molested.
Remember, the owner is a mechanic and probably had access to a complete later model car that was destined for Sultan ka khu...it being a slow work week he probably decided to upgrade his own car by taking parts off and using those from the donor car. ...how far he went is any body's guess