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Here's a treasure trove for you. You can find a good top end refresh guide, along with many other great guides, here: http://dwaynesgarage.norcal928.org
Cheers
+1 on the Dwayne's Garage reference.
Also, Scott Yoo did a very good documentation on his 1986.5 top end refresh, (which is very similar to the 1985, especially the plenums.