High Idle issue - mild 360

31 degrees initial timing? If so that is a bit high for a mild build. I have a moderate build 360 and my initial timing is about 15 degrees.
Also closing the hood and having your rpm increase is indicative of you running lean since you're restricting the airflow to the carb once you close the hood coupled with high initial timing I'm surprised you're not pinging like mad.
That is if you indeed have 31 degrees initial timing.