Can anyone help me with the Make, Model (version), and Unit of this WWII army trainer. Appears to be an AT-6 version
That is a North American NA-36, BC-1, a North American NA-16 derivative, the predecessor of the  North American T-6 Texan

Source: nationalmuseum.af.mil 
Some observations that helped to determine the precise model:

The fuselage is covered with fabric. Later models used metal

The trailing edge of the rudder is rounded, later models had a straight rudder

The bottom corner of the rudder is squared, some other models are rounded (e.g BT-9)

The fuselage shows the crest of the USAAF's Technical Training Command:



Source: Picturing Meteorology. The text &quot;Sustineo Alas&quot; is latin for: &quot;I sustain the wings&quot;, or more loosely translated: &quot;I keep em flying&quot; 
The aircraft belonged likely to Chanute Field Technical Training Command (Illinois), located some 200 miles south of Madison.