When you mentioned shims in one statement did you mean shim head gaskets to get valve clearance, and in the other statement just mentioned spring shims. I might have read that out of context? and thought you mentioned valve spring shims to get valve clearance?
Any way a lot of machine Shops (the good ones) will stamp the deck ( mark it)!! When you clean the deck look for the marks like .004 or .010 etc if its not marked do like doublevision said and look it up there are a lot of good tech articles that cover this and would save us a lot of typing
I type really slow and hate long answers!!! Theres probably a thread already on hotrodders covering this, do a search!