FoC
You should be well into a focussed rehab program not only concentrating on your neck but also thoracic and lumbar spine, rotator cuff and scapula stability. Someone also needs to be pushing your thoracic spine respectfully around.
We normally get people running by 4 months, but are guided by symptoms pre and post op, control of your head on neck, running stylee and foot posture/shoes. Distance also plays a big part.
It's very rare that running will give you problems BUT it's how you run that potentially will...
Good Luck with the recovery, stay ahead of the curve.