Have the tie rod ends, pitman arm and idler arm changed that will cure your issues.

Nice truck. I have a 98 Pickup.

That front end is from a GMC. Not sure if they sell GMC in Mexico. In the states GMC has that big open grill where Chevrolet had a fat bar going across from side to side splitting the headlights from the parking/turn signals.

What motor is that? It doesn't look like a Vortec 5700.