Out here in Quartzsite AZ and had to fire up the furnace for the 1st time. I want to install an extend-a-stay type connection so I can use a larger tank but DON'T want to use the furnaces due to them ...
You should be very careful with rearranging blocking, moving ducting. Furnaces are designed for a certain amount of airflow. To much or to little can create problems. Especally to little which can cause overheating. There safety limits that help with this but even those can fail and allow an overheating situation.