I have removed an AC pad without taking out the frame, more than once.
It can be done, but you won't be able to get to the speed nut up between the defroster vents. I removed all nuts, but that one. I then lifted up on each end of the dashpad, and pulled and twisted. It eventually snapped, and I was left in the back seat with the dashpad in my hands.
A Kodak moment, for sure.
As was mentioned, the gauges, ashtray assembly, and glove box liner need to be removed first. There are also screws on the outside of each end of the dashpad. I'll stand by my usual credo... If I can do it, anyone can.
Mike