Brother hassan_mirza9, beware of the customs anti smuggling department. They will detain your car sooner or later. After body change you need to deal with them for custom clearance.
I have personally been through the whole cycle and I advise you to workout the clearance plan before you invest your time and money on new body and its conversion. You better avoid body change or get ready for all the hustle and tension of custom clearance. It might look easy but let me tell you it is not.
Last but not the least I want to let you know that it might happen that your car never get out of customs. This will happen if your car fails to clear the forensic laboratory test and that is a MUST before customs allow you to pay the duty for newly changed body. So think twice before you go for the body change.