I don't know what spring anchor is either but we will both learn from steve-H. I should have said "because you were unable to bob and mark". Not your fault. Straighten your spindles and measure each side. NOW use a plumb bob to mark each side of frame, then use bob again on each side to align center of axle tube.
I'll ask again to be certain - I'm measure from the front spindle/kingpin back 116"?
