One of the things I did that I would highly recommend is to make the dashboard assembly removable after the body is installed and the gauges/switches all installed in the dash. When I wired the car the body wasn't installed so I could get behind the dash assembly from the top for easy access.
First was to cut the lip off the dash at the top so you can slide the dash downward during removal. Otherwise it would hit the dash cowl and you couldn't get it off the dash support on the "birdcage". Second, during wiring, I added several Molex connectors for the wiring going to the gauges/switches so they could be disconnected. That part was pretty easy as there are several little groups of wires and it was just a matter of adding a multi pin connector with pins that go wire to wire (or color to color). I didn't worry about the wires for the light switch as you can just take the nut off that holds it to the dash.
The only real issue is the "choke" cables that operate the fresh air dampers and the capillary tubes/bulbs for the mechanical oil temperature and water temperature. I just made sure the grommet they go through was big enough for the bulb/nut.
There were a couple of reasons I wanted to be able to remove the dash assembly. One was that I am taking it next week for final body work and paint. I didn't want the gauges/switches to get screwed up with sanding dust or what ever during the painting process. Second was if I ever needed to fix the wiring or add any electrical items I wanted to make sure I could remove the dash to be able to access everything without lying on my back trying to access stuff up side down. I'm way too old for that.
Anyway, in preparation for taking my car for painting, I removed the dash today. Had to remove the steering wheel, upper steering shaft and steering boss so the dash would slide down. Everything work just as I had planned. Dash came out without issue and didn't take much time at all. As a added benefit, when it comes time to install the windshield wipers in the cowl and the hood hold down brackets with nuts behind the firewall after painting, everything is easily accessible. I would have hated to try to install things blindly with the dash installed.
I highly recommend that anyone building their cars consider making their dash assembly removable. Here is a picture of the car with the body installed and the dash removed. Easy access to everything.
As a side note, I'll point out the dash support tubes. Note that I have mounted the assembly with a bolt to the bracket on the "birdcage" with it on top. That is so when it comes time for carpets, I can remove the support tubes by removing the bolt and pulling them up, cut holes in the carpet and reinstall the assembly. Otherwise, I would have had to cut the carpet all the way to the edge to go around the tubes. Just a little recommendation that might make it easier.
Russ