If you look at the adjusting method for the main shims, you remove shims until drag is created and then replace one shim on one side. The shims are .002" and so that translates to a minimum of .001" clearance. The GMC engine which is different but similar calls for .001" to .003" clearance on a new assembly.
For the rods, a similar method was used. There were .002" shims and .001" shims so in theory you could be talking a minimum clearance of .005" on the rods. I don't think that you want a rod to have a clearance greater than .003".
I shimmed my rods before I installed the pistons on them and this way I was able to get a handle on the drag.
