I found these shims to be readily available on ebay. Forgive me moderators if this is the wrong spot for posting this but I wanted a little more response. I contacted the vendor and this company seems to be pretty capable of getting whatever type of shim for doing the xt6 alt swap on the ea81 or ea82 type cars. I thinking of ordering some soon enough from this company.

 

http://cgi.ebay.com/Delco-Remy-Alternator-Fan-to-Pulley-Spacer_W0QQitemZ250025368353QQihZ015QQcategoryZ33573QQrdZ1QQssPageNameZWD1VQQcmdZViewItem

Early Maxima alt's are the same power as the XT6 but bolt-in. Same deal with swapping the drive pully though.

 

GD