How much decking is to much?

It is a little complicated when using a custom small block crank (2.96" stroke), custom rods (6.298" center to center length) and old school TRW pistons (This is the 305 motor I am building),

I told the one machine shop to set the TRW L2322 dome pistons to .017 above the block deck (rated up to 12:5 to 1 compression). When they got there, one deck was still not cleaned up, so they made a small second pass. I am glad they did not remove any more material from the other bank that had already cleaned up with the pistons set at my specs. I can either run two different head gaskets, or not worry about it and run the same gasket (after verifying piston to head clearance, of course).

The second machine shop is working on a factory 340 high compression motor (flat top pistons). They cleaned up both decks on the this second block, but like I said, one side needed two cuts. When I assemble the rotating components on the second motor, I will see how the piston deck height compares, bank to bank. Should be interesting to see if both blocks were "off kilter" in the same way. Regardless, I don't want either shop taking off extra material (that I could never recover) from the cylinder block deck surface. And if the specs differ by only about .005", that still seems to be much closer to blueprint specs than the factory output.

One more factor to consider is the final compression ratio of the L2322 pistons in the first motor (de-stroker). According to the on-line compression calculators, de-stroking will lower compression about 1.5 points, depending on combustion chamber volume.