Lower a arm position

[Kaptain Kadian]

I am in the middle of putting in my new disc brake conversion and noticed the placement of the lower a arm. I have always had problems with my headers and space on my frame. It seems like the shaft that attaches the a arm to the cross member is pushed pretty far back. Is there a way to know where that is supposed to be? I want to clean up the a, arms and cross member and coat them with chasis paint while I have everything apart. Man, everything was dirty. I pulled a bunch of caked up grease out of the upper a arm.