We decided to run a little experiment in our kitchen yesterday. We monitored our turkey's temperature with two probes - one in the thickest part of the breast meat and the other in the center of the stuffing (we stuff our bird with home-made bread stuffing). The temperature of the stuffing lagged the temperature of the meat by 10ºF. When the breast meat reached 160ºF (71ºC), the stuffing was only 150ºF (65ºC). We checked the probes against each other at that point by removing the stuffing probe and transferring the meat probe into the stuffing. They agreed within 1ºF, so we simply continued to monitor the stuffing temperature.
USDA recommends cooking poultry (chicken, turkey or whatever) until all parts of the bird and its stuffing reach 165ºF (74ºC). If you have only one temperature probe and you stuff your birds, the best place to monitor cooking temperature is in the center of the stuffing.
One last reminder. Refrigerate any leftovers promptly - don't wait for them to cool to room temperature first - and, preferably, in shallow containers so that they cool quickly to 40ºF or below.