A lot of us used to deck blocks to squeeze every bit of compression out of the motor we could. Using steel gaskets (painted with copper high heat paint to help them seal), a set of pop ups (like the Manley 12.5:1 compression pistons I ran), and a .012-.015 deck mill to get the pistons right to the deck surface, and enjoy a good performance gain from a near zero deck. Course, you had to watch piston to valve clearance, and not get too wrapped up with a monster lift on the cam, but it was a good performance mod back then.
I've seen pistons pretty far down in the bore on factory blocks, as much as .020 or better depending on the performance level of the engine.
Regards,
Steve