Noman Saheb, I would like to suggest something if you don't mind.
Vehicles are to be used: not praised or appreciated or kept in showcases.
So, it is very convenient to have a vehicle where all the spares are easily available.
Stretching the vehicle will change requirements for leaf springs, for balance rods, or whatever mechanism your vehicle is using for keeping the tyre on the ground, the driving shaft, etc.
Brakes, and other minor adjustments are also important.
All this at a cost....
And please calculate the advantages you are gaining after all this trouble...
and if you wish to sell it off any time later, ...... Bang...
So, please do consider it.
If you wish a longer chassis vehicle, pl. go for original long body Suzuki, or a 5 door Vitara, or Daihatsu Rocky, .... or .......
the choices are unlimited.
Once the body is original long chassis, then you can work on the upper shell, and convert it into soft top or targa top or something else....
Irfan Khattak