Models differ slightly depending on the country they are in, so let me try and answer you this way:
The 60, I assume is the station wagon.
It is more comfortable to drive than the 70. The aircon is way more efficient if it has one. It is easier to plan and utilize packing space. It is a vastly capable vehicle and there are many of them still around in Africa, so you will have no issue getting spares.
The 70 we have is either a pick up truck or smaller station wagon. If the 70 you are referring to is also called a "Troopy" or "Troop carrier" it is a beast of a machine and very sought after. The only down side for me there is the automatic gear box. One of the reasons is that the Jap models do not have adequate cooling systems for their auto boxes which can be an issue in very hot conditions. If it's a 70 station wagon, it is quite a bit smaller than the 60 and if it's a pick up, your lack in space in the cabin will frustrate you when overlanding.
Both these vehicles are reliable and great for overlanding. You will not find it hard to find spares for either and they are equally capable.
The three biggest expenses are the long range fuel tank, heavy duty suspension and double spare wheel carrier at the back.
The best long range fuel tank for Land Cruisers are made in Australia by a company called "Out of Town 4x4" and the tank is called a "Longranger" It is honestly not worth setteling for anything less as a split fuel tank in the desert or jungle can have a real bad outcome to your trip!
Any of the known after market suspensions will be fine. You'll need 600kg springs in the back to carry the extra weight of the fuel, tank and spare wheels. The standard suspension will not do.
For anyone who wants to do it cheaply and try and save money and cut corners: Read this story before making up your mind: The Ollie and Cat Story...