Doing Africa in a '79 LR S3 88''

[MarkusK]

I plan to do Africa overland from Germany to Cape Town, starting in spring 2005. That's still a long time ahead, but it'll take me a while to save enough money for a new start after my return and also to do the trip which I plan to last for about a year and a bit without any financial problems.
I plan on doing it in my '79 S3 88 which seems feasible.
The car is in a very good state. It was actually imported from somewhere in Africa, whre it's been very dry, i.e. there's no rust on the chassis, etc. It's sturdy and the dents in the body make it look far worse than it is.
The engine is new, just being run in.
I do all maintenace myself, I've got a good collection of tools and all the repair-manuals.
I've got a cyclone-filter which still needs to be fitted to the car. Also, the car is equipped with tow spare tyres, one on the bonnet, the other on the rear door.
Then there's a stury roof-rack with wooden planks which is also suitable for holding sandboards on the sides, etc.
In addition to this I plan to do the following alterations to the car which seem a good idea. Maybe someone with more experience can give me some good advice on this:
- I plan on putting in a double aluminium floor in the loading bay on the rear, approx 10cm high for holding spares, tools, etc. There would be a sort of sturdy drawer for the tools in the back part, which would only be accessible if the rear door is opened.The front half would be accessible from the inside, for spares, gaskets, small stuff.
Also, there would be a small hidden compartment there for valuables, cash, etc.
As it takes quite some trouble getting in there and things aren't visible from the outside, this might be a good protection against theft as well.
- On one side I plan to mount a foldable bed made of aluminium which can simply be folded together and the up against the side.In order to use it you would have to put forward the backrest of one front seat, the front end of the bed would then rest on the dashboard. The bed would be just broad enough for a thermarest mattress, which should do for sleeping in the car. Beside this, I plan on mounting a roof-tent, which is far more comfortable if you're somewhere safe.
I've got some water- and even airproof aluminium-boxes (made of 5mm cast aluminium) from an army surplus store. These sould do fine for holding cameras, films, etc.
Hmm, what else...
I've got five 20l water-canisters made of plastic with the same dimensions as Jerry-cans as well as five 20l Jerry cans for Diesel.
Would that be enough or need I take more?
I'd need to store them somewhere. Here in Europe the car will consume around 10l/100km, which would give me a radius of approx 1.400km. Given that it might consume double as much going rough, I'd still have a radius of 700km. Would that do or should I take more?
In order to keep the heavy items as close to the bottom of the car as possible, I'd store them on the inside and put some of the lighter things in my aluminium-boxes which are bolted to the roof-rack.
Is that a good idea?
Which spares do I need to take besides the shafts for the axles and spare springs (I don't mean basics like fanbelts, etc., just the serious stuff)?

Hmm, those are lots of questions and I know I'm planning far ahead, which is why I won't ask any more.I'd be glad to hear from others who've got experience doing the trip in an S3.