how to correct castor on lifted straight axle suburban

[orange72sub]

Hey guys I am building my dream truck a 1972 K20 suburban, it already has a 4-6" lift on it. The truck is a handful when driving down the road. It rides on 35"x 12.5"x16.5 BFG all terrains. I am going to do a cross over steering upgrade from ORD. But still think something needs to be done with the castor to get the truck to want to stay straight and not continue to wander all over the road. I know I need to keep the drive shaft angle as in line as possible to keep from wearing out the universal joints. Do I have to have the axle knuckles cut off and rotated to fix this? What degree of angle should I have them reset too if so? I don't plan to off road this truck but I do plan to drive the wheels off of it figuratively that is. I would like to know that my son or wife could jump in it and feel comfortable about them being able to drive it. Any help would be great thanks!