Hiya,
I have the LC200 Altitude on 18" rims. I looked at swapping to 17" but the changeover was prohibitive. In all reality if you blow a tyre in remote you will be waiting for delivery of a replacement for 17 just as long as an 18.
Anyway, I upgraded to 3800 GVM with Dobinson springs and Bilstein shocks plus polyairs.
I run Cooper ST Maxx at 275/70/18 and have been very happy with them. Last January we did 6,000km towing including lots of 4wding and beach driving and averaged 20l/100km or thereabouts. Our KK fully loaded with tinny, outboard, folding trailer and water etc is close to 2000kg so we have a heavy rig. Economy around town at home is about 14l/100km and I have roof racks plus drawers and fridge in the back full time.
I'm hoping that by the time I changeover the tyres, there will be more to choose from for the increasingly common 18" rim. I have the tyres rotated and balanced every 10K km as per manufacturer instructions and warranty requirements, which hubby thinks is a waste of time and money coz if you add that up over 80,000km it probably covers the cost of a tyre or two.
I changed the tyres the day after I bought the car and traded the Dunflops it came with. Got about $250 per tyre from memory.
I also have the Opposite Lock premium loop colour coded bullbar as I'm not a fan of our local ARB store and in fact I like the loop bar better (and my car doesn't look like every other 200 on the road). Check them out, I reckon they look the goods. Opp Lock also do a post bar similar to ARB.
I also have a 9500lb VRS winch which we have used several times to get ourselves out of trouble. If you're serious about getting off the track, then put a winch on.
More info on my rig here:
http://www.myswag.org/index.php?topic=32574.0Hope this helps.