I would recommend getting pistons with the proper compression ratio vs milling the block and/or heads. If you mill the block and/or heads, then you may need to mill the intake so the ports will line up properly. :sad1:
Get the proper pistons if you haven't already bought them to save the headache of milling the block/heads and intake. :banghead:
That's a nice street cam that you've picked out, and these guys are steering you in the right direction.