Funny you should make this post - I have a 70 RR and just completely removed the harness on Saturday, to clean it up and renew some connections.
I have it hanging from the ceiling in my kitchen - should have taken some pictures.
It really wasn't that difficult, and I only removed the gauge cluster and the 2 kick panels, (and the neg battery cable of course) then labeled some of the connections with masking tape.
Removing the connection block from the firewall was much easier than I thought. From under the hood I disconnected the 3 plugs, then to remove the block on the end of the dash harness from the firewall you just have to use a screwdriver to push down the 2 metal clips on top of the block - the block can then be pulled into the inside of the car.
My car doesn't have AC, but other than that my harness is probably just like yours.
Easy to remove, just takes some time and patience.
Hope this helps.