AC: you can unbolt the whole plastic piece from the firewall for now, and if you are TRULY getting rid of the AC, you will realize, as I did, that the entire ac system is able to be removed in one big chunk, and stay charged. its crazy, but true, you can unbolt the compressor, take out the radiator and then the condensor, and leave all the lines hooked up and whoop. it all comes out together.
wiring: the big firewall connector at the drivers side upper side has two plugs in it, one is to the rear lights and fuel tank. the plugs are together in a larger connector though that can be taken loose by using a small flatblade screwdriver to release the catches from the firewall side. you may have to remove some sealant to get the large connector detached. once you have it loose, you can separate the rear harness wiring if you like or leave it attached. then there are two 7mm bolts exposed that hold the inside fusebox and wiring to the firewall.
here is a picture after both steps, you can see the connector hanging and the hole where the fusebox would attach from the inside.
brakes: you can take the 4 nuts off, the saucer thing is the brake booster. you will need to disconnect the shaft of the booster from the pedal, there is a pin clip you pull and the shaft slides off the pedal. then you can pull the booster into the engine compartment so its free of the cab holes.
I recommend you take a cut off wheel and carefully cut out the fusebox mount and the booster mount section of the firewall to use on your AD cab either as patterns or instead of cutting holes. thusly
there is more wiring on the passenger side for the TBI ECM, and a bunch of grounds, take your time and DONT CUT. mark as much as you can with strips of tape, just mark each side of the connector with an "A-A", "B-B" etc, with one letter on each side so you can see what plugs to what. dont worry about the gauges just yet, lots to do. I left the dash harness in the dash (it unplugs) until I needed it.