My Dear Brother.
Keeping in view my experience, it is not possible to convert an older model to latest model. It would be appropriate if you go for restoration on same model or shape.
Bcoz if you restore it with latest shape, at the of the day you will end up nowhere.. It will eat a lot of money without any value.
If you want the newer look.. Buy an auctioned Defender 2003 onwards. It will cost you around 5 lacs.. Then even if you spend a million on it.. That will be worth to spend.
Best of luck