Most pizza factories i know of are using a blast freezer for precisely this reason
Once they are packaged and then put into cardboard cartons, the laws of thermodynamics require for first the item to force the "heat" out from the middle, and then the cold can infiltrate from the outside in (much like a roast of beef but in reverse)
The need to be at or below 10F BEFORE going into the storage units, and that will happen even faster if you do that prior to packaging
If you have the floor space, you can add a length of blast freezer to the conveyor system (not cheap)
OR you can put them on some sort of open air raking (covered) into the freezer you have, until they are at 10F, then package and palletize.
something like this http://www.fpscorp.ca/iqf-freezers