I don't know who told you it would be easy, but it isn't. Adding a lift to the vehicle would be a piece of cake compared to converting it from 2WD to 4WD. But if you are a very experienced mechanic, a good welder and fabricator, and have more time and energy than you know what to do with, have at it.

But I'd be willing to bet that before you're halfway through the project, the thought will come to you, ""Maybe those guys had something there."

It's pretty clear that you want to do this project. I'm not sure why you asked for advice, and then resist that advice. But at the very least, you will get a lot of experience working on off-road vehicles.