I should really write this up more fully and post it on my website once and for all... but till then, here is a short version of what I consider to be my "standard advice"
Figure out what you "need" for the trip. Divide that by 2. Then take out at least 10 things. Then take out 5 more.
Ok, now you are almost packed.
Whatever mods you've done to the truck, great. Now stop.
Fix anything that is broken (definately your oil problem)- but anything else as well. If something like brakes is going to encounter it's normal service interval while you are on the road, why not replace it now, before you go? Certainly change out all fluids (tranny, tcase, diffs, brake, clutch, radiator) and all filters (air, fuel) before you leave. Carry at least one spare of each filter.
Add a rooftop tent (don't argue, you'll thank me later).
Make sure you have a good way to secure stuff- I liked Balum's idea of truck boxes, but he had to pull his rear seat, which I didn't like. We used a roller-drawer and a Tuffy console and a LOT of care and had no theft. If you pack lightly (see above) you'll find it much easier to secure things and you'll be less of a target.
With the money you've saved on not making major engine mods, pay extra for secure parking whenever possible. Treat yourself to a decent mechanical checkup whenever you spot a Toyota dealer (there will be plenty). If they find something there, it'll be worth a lot of money/time/hassle/heartache saved vs. finding a problem in the wilderness.
Find someone to accompany you. Lonely Planet's website used to have a bulletin board for people in foreign lands to find other people... I'm sure plenty of backpackers would LOVE a ride.
If I were to do the trip over again, I would drive a diesel cruiser with a rooftop tent, OME suspension, 31x10.50 tires on stock rims with 3.73's (stock gears). Add a set of lights up front and a set for reversal. Tuffy and roller drawer inside. GPS receiver. That's about it for vehicle specific stuff. The rest is camping.... everyone has their own list of what is good for camping, but less is often more. A couple of things we learned to love: Candle Lanterns (REI.com has them) are great- bright enough, not too bright, and add a ton of heat to a rooftop tent at night in high altitude. A good way to boil water is key. If you have a water container that is just bigger than 5 gals, you can always grab a 5gal bottle of water and fill it up quickly- most places charge a deposit for the bottles and you can't use the "wrong" bottle as an exchange if you change areas/countries. A second, smaller water container is a good idea- back up and whatnot. We carried 10gals and almost never needed all 10 between fillups.
As said above: a 12v Hella Turbo Fan might just be the best $50 we spent on gear. I would consider buying two....
Feel free to PM me or send an email to steve at sandcruiser.com for some more thoughts.
The key is to remember that a stock LC could make the entire drive just fine. The more you depart from stock configuration, the more likely you are to break things and/or be a target for theft.
The trip is wonderful. The people are fantastic (generally). The journey is worthwhile.
) but you can buy a 1HZ/1HD-T ( with 30 - 80k kilometers ) with tranny ( manual ) in 3000 - 40000 it depens off course the overall shape of the engine and luck ! 
also Bariloche
