Help with Vintage Air Vent

[Mondo]

I'm taking apart my dash to paint it.... since I have to replace the wiper motor too.

I've taken the gauge cluster, dashpad, radio etc.. out but I can't get the passenger vent to unscrew (no room to reach back in there). It's very tight right there and I'm not sure what to unbolt etc..

If someone has installed their's maybe they can remember the assembly order and can advise if I can just take the fiberglass box out (it looks like it was put in before mounting the unit..? It's pretty tight up under the dash and I don't know what's what.

I'd hate to have to try and mask that vent for painting...

I found this in the search
http://67-72chevytrucks.com/vboard/s...ad.php?t=61810

I didn't try too hard to take the fiberglass glovebox out... thought it went in before mounting the unit but there's a picture here with it out.
Anyone know if I can wiggle that box out.... it would definately give me room to remove the vent?