Been dead set on get Mahle 346 -4cc pistons..why are they .007 smaller then everybody else? I just dont want to bring the wrong size pistons to the builder

 

3.898 vs. 3.905?? The 3.898 should fit a stock block where the 3.903 and 3.905 pistons are for blocks that have been bored/honed .005-.007". I would ask the builder if he recommends going oversize or if the cylinder walls are fine.