Removing AC Vents from a 68 Dart

So I want to remove the AC Vents from underneath my dash. I don't have an AC compressor or condenser, my hoses are hard, the plastic is rotted pretty bad making the vents useless, he AC buttons hardly work and get stuck, and frankly I'd rather mount the radio under the dash than in the glovebox (making the glovebox useless at the moment). I just don't know where to start and am having trouble finding the mounting points. I started to unscrew the dash cover around the vents but where do I go from there?

That dash:


How it sits now:


The damage: