340/416 piston question.

Just add the compression height of the pistons you're looking at to the rod length (6.123) plus 1/2 stroke and you will know where they are. I'm guessing they (stroker kits) usually shoot for 9.578-9.6 (deck height).
A quick perusal of Summit shows all 340 stroker pistons they have at 1.459-1.460 which will put them just at or below stock deck height.