Always fully cook the stuffing BEFORE putting it in a Heritage bird. 

Use a good quality meat thermometer placed in the thickest part of the thigh to determine when the bird is done.  Do not depend solely on cooking time!

Start closely monitoring the temperature at least 1.5 hours (1.0 hours for smaller bird) before the cooking time estimates when it will be done. 

Once the temperature reaches 145 degrees watch it very closely as it can rise quickly.

Plan on 1 hour of cooking time for every 7 lbs of bird - but use this just as a guideline.   Cook by temperature!