In some markets the IFS 100 series was available with the 4.5L I6, Erik has/had one.
That's handy info to know Jon, thanks. So when looking at a 100 series it'll pay to look at the front axle, engine and vin plate, to actually see what your looking at. I don't know if Australia was one of the markets that got the 100 with the 4.5 straight 6, but with how the imports have worked their way into various countries over the years, it can get a little confusing. The only 100's I've seen in Oz have had the 4.7 V8 under the bonnet.
Some further thoughts. My 105 is (as Ed originally said) an auto, which is my preference, but auto gearboxes do add to the fuel consumption. I find that running the air conditioning does make an noticeable increase in fuel consumption, especially in the heatwave conditions that we've been experiencing over the last 7 weeks. Our usage has also been a little heavy on fuel, as we've been driving our loaded 105 on steep mountainous roads, dirt roads, and heavy going 4WD tracks with lots of low range gear usage, but after all that I'm still happy with the consumption that we're getting. With our 240L of fuel in tanks the car has good range, and has never come close to running out. If it just had the 90L tank then that would be a bit of a handy cap, but when we bought ours it had the 90L main and 50L sub tanks, which I believe it left the factory with. I'm not sure which Australian land cruisers came with this set up from the factory, but it's worth having if possible.
When I was looking to buy, I was advised to keep clear of LPG'd vehicles as most have older LPG systems don't lubricate the valves, allowing premature wear of the valves seats etc, the remedy, a new head $5000 approx. Plus LPG would not be available at some of our destinations. As I perused the ads I started to notice more and more LPG land cruisers that had had a replacement engine, or recent new head. Makes you wonder why they are being sold, and if your buying someone else's trouble.
Be wary of some of the cheaper diesels on the market in Oz, mostly they are the normally aspirated 4.2 diesel engines, which are fine as long as you don't want to get anywhere in a hurry, and could prove a little asthmatic in hilly country with a caravan on the back. The majority, if not all the 105 series will have the 4.2 NA engine (HZJ105), where as the 100 series normally has the more powerful turbo diesel 4.2 engine (HDJ100).
If you find a 4.2 NA with an aftermarket turbo installation, make sure that your happy its been done correctly, and the boost isn't wound up too high. As I'm always weary of a NA engine that has been turbo'd, but there are plenty that have been in Oz, so again, the local forums would be able to give a reliable reliability prognosis.
For towing and occasional dirt road use, I'd be looking at a petrol or diesel 100 series auto, depending on the budget.
Where about in Oz are you? (If you fill in your location details, it'll show up when you post) As a friend of a friend near Brisbane is looking to part ex his petrol land cruiser, I'm told its in great nick and has 230,000Km on the clock, but I don't know if it's a 100 or 105, or any further details. It just came up in conversation last night.