surely it would be way easier to buy a LHD series III from Jacksons for £150, get someone to donate you £50 and bob's your uncle an LHD for £100 and no fannying around converting one to tuther. S'wat I would do.
I think for 150, it'll need a bit of work, but any lanny at that cost is going to need work to get it to africaland in 2008.
I'm doing the same in a more modern (1989) Ninety, but to be sure of getting there, I'm having to redo so much and Im doing it all myself using free or very cheap salvaged parts. It's still cost me £1600 and that's not including the purchase cost (or indeed a new chassis, but that's my fault for buying one with a shot chassis).
Unless you get donated a good car to begin with, and donated a load of stuff to do work and prep it, and do it all yourself for free, I can't see you getting there in a landy. That's just the way it is. No way. You'll end up breakin down and needing recovered or abandoning it somewhere... remember a desert is not a good place to breakdown!
On a hundred quid buy a cheap modern bulletproof 2wd car chuck a bashplate under it, some bigger wheels and tyres from a scrappy - and that might do it.
Good luck though - it'll be an adventure