I'm waiting on OSG LSD and have been researching this like you. The general consesus seems to be that you wait on shims until you measure the backlash. Most people seem to end up not needing them.
Best DIY i've found so far.
OS Giken Super-lock LSD Installation - MY350Z.COM Forums
I like this one too.
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And don't forget this one:
DIY: Whiteline rear differential bushings