HELP removing LH AC vent tube

[SilverMiner]

I need some advice or tips on removing the lower left hand AC vent (and tube) that sits next to the headlight switch.

I have removed the 4 screws that immediately surround the vent as well as a support strut that sits just below the steering wheel, and yet I can't seem to get the assembly out from under the dash.

Before I get too "strenuous" with it, I figured I'd check in with you guys to see if there is another attachment point that I have missed. It appears to just slip over the main vent box that sits on the transmission hump, and I've been unable to find any other attachment points, so your advice is greatly appreciated.

FORGOT TO MENTION this is in a 1980 Suburban.