The first thing to do when preparing your Land Cruiser for an overlanding trip is to think long and hard about the sort of driving you are going to be doing and the terrain you are likely to be crossing.
The chances are that most of your journey will either be on tarmac or on local unsurfaced roads that the locals are driving on in beaten up old Peugeot 504s or Mercedes saloons, in other words the sort of conditions that a bog standard Land Cruiser will take in it's stride.
It is for this reason that we feel that the most important part of your preparation should be spent ensuring that your LC is capable of doing the trip before you start thinking about bolting on all the extra goodies like roof racks, bull bars, etc.
We therefore recommend that before all else you should 'Baseline Service' your LC to ensure that it is mechanically sound, and then progress from there to improving it's offroad capabilities for the occasions on your trip when you want to drive off the beaten track.
It is only at that point that you should start thinking about all the extra kit you want to have bolted onto the LC to increase your range, carry extra equipment, and generally make the trip more comfortable and enjoyable.