Besides the spacer, there are a couple of other things that suggest to me that this A-arm has been removed and possibly repaired:
a) The mounting hardware for the lower ball joint on the LH side is reversed in relation to the hardware on the RH side (lock nuts on top of LH A-arm vs. lock nuts on bottom of RH A-arm). While this could simply be an oversight, Brain Anderson was the original builder, and Brian, as methodical as he is, would have most likely assembled the A-arms side-by-side (at the same time), the same way.
b) The LH A-arm paint/powder coat has a dull sheen vs. the RH A-arm is reflective (perhaps a clear coat). This difference may be due to shadowing, lighting, etc., but worth a look.
'If' the A-arm/shock mount has been damaged, the best course of action might be to simply replace the A-arm. Loren Edwards (aka, WestTexasS2K) should be able to help you out with a replacement.
X