K20 Suspension question

[Jack15T]

Hi Folks, I have a 71 K20 pickup that I am installing new front springs. I have seen several exploded diagrams of the front suspension. The diagrams show a spacer between the spring pad and on top of the spring underneath the mounting block. My new springs centering bolt head is to short to use a spacer with. I suppose I could get a longer one. There wasn't a spacer on either side of the spring pack when I removed it. The local spring shop that sold me the springs states that I don't need them. The only thing I can think of is they are used to adjust the ride height or they are shims to set the caster. Any ideas? Thanks, Jack