Hi Gazzer, I’m not to hot on foreign languages, bit I’ll give it my beast shot!
On the 80 series, which I understand to be as close to the 105 as makes no difference, a 2” lift is about the limit without needing castor correction.
What I suggest, before you modify anything, is to get an electronic read out of all your alignment angles, from a modern tyre fitting workshop.
Once you have them as a base, you can modify (within the limits of the state where the vehicle is registered) and know which angles you’re trying to maintain.
Caster correction can be done with offset bushes (not highly recommended), with correction plates, which I’m told are good for lifts between 2” and 4” and for anything higher, dropper boxes are better, which drop the trailing end of the radius arm to maintain the angle. You can of course go the more expensive route and get new trailing arms, which are specially profiled to maintain the caster angle on higher lifts.
Where are you, how long have you had the truck, and how much do you know already? These are questions you could answer in the introduction section of this forum, it’s good for other members to get to know you and your truck a bit, so I suggest you post an introduction of yourself, your truck and give us a bit about your background, and some photos if it allows you to post them.
Welcome aboard by the way
Great truck, the 105 ... BTW