The reason they probably say they aren't to be used for the black top is that the Cmopression chamber volume is not the same as the silver top, and that the stated Compression ratio would not be correct. The squish areas for Blacktop and silvertop are different - if you look at the piston top shape on the factory items they are quite different. I can't see any harm in putting them in a blacktop other than the Comp ratio being a bit lower.
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