I've crossed into an area I don't really know much about. i got several heater boxes awhile back with some parts for my Cuda. This was out of a 72 GTX? I believe ? I've heard it may be a Strato vent box? What was the purpose of the Strato vent heater box. I've been researching Google but there must be some knowledgable folks on here that may know more.

that is not a strato heater box..
it is a non ac heater box.

Was the Strato just for AC units?

no
strato was a extra fresh air vent
that ran off of the heater fan.
it was popular with 4 speed and hemi cars that could not get ac.
there are a few parts that make up the system
the heater box
dash applique that only had 2 center vents
ac cars had 3 vents
non ac had no vents
the heater controls were also specific for it.
plus there is a special vacuum water valve
located on the heater hoses.
if photobucket didn't screw me up
i could post pics as i have the complete set up for my car but the bucket screwed me up.

I agree with flypaper. It was just an extra air vent. The stratovent was opened/closed by vacuum actuator and like he said there was a vacuum actuated water valve that shut off coolant to the heater core.

PS That doesnt fit an E body

Find any PN on any part on it and google it.

the added feature of the "STRATO VENT" was a powered (blower motor) fresh air vent

I have better pics of this one from a '72 GTX (I'll see if I can find them), here's the part number & date