I have a 90 k1500 that i am getting ready to do a sas on. I have a hp dana 44 with all the radius arm crap cut off the tubes and i need to set it up for leafs. How do i go about welding on the spring perches i am kind of confused about how to set up the caster to the right amount. also what determines how high up on the frame the rear spring hangers go on the frame am i looking for pinion angle or is caster also a factor?