To the OP of the thread, here are the questions you should be asking yourself:
1- Can it be done? Yes it can.
2- Is it very complex? Not as complex as you think it may be.
3- Has it been done successfully before? Many, many times.
4- Is there any draw back of this conversion? None at all.
5- Who should carry out the conversion? No one in Karachi, Lahore or Pindi/Islamabad should attempt this. The best people to do it are the people who work on body changes in Quetta and Peshawar. Anyone else and I guarantee you they will mess it up. These guys, the guys who do the body changes, have done these conversions many many times. Its a walk in the park for them.
6- Should you do it? Absolutely, you will love your Gen 1 after its new rear end. While you are at it, do a rear disc brake conversion too. Please remember, none of this is as complicated as it is in the Toyotas. No pun intended, but seriously, it is not rocket science. Remember to put on some heavier springs in the rear, don't put up the genuine Pajero coils as they are too soft. Better to go for 5 door Intercooler coils at the back. Thank us all later. Now run along to Quetta!