Reassembly Questions regarding firewall

[Patrick brophy]

I am starting to put my 1957 Thunderbird back together and I have a few questions.
I did not take a good deal of the car apart, so I am flying in the dark as I reassemble it.

I just put the dash back in the car and I am attempting the run the wires and cables thru the firewall.

I have a large hole where the bushing with several holes (4) goes and I know the wire harness with the two separate wire groups goes there. I do not know what else goes there.

On the lower left of the inside firewall there is a large opening in the firewall insulation pad (see photo) inside of that opening there are two small holes in the firewall just above the dimmer switch. I am assuming that one of those is for the left hand air cable. I have no idea what the second hold is for, and I can see no mention of it in any of my many manuals.

I hooked up the tach cable. It appears to me that it is a little long, almost to long. Is there several length tach drive cables for the different Ford models?
There is an electric connecting block that is located on the front left inter fender. I am unsure of the way the is fastened to the fender. There is a brass insert at each end that are threaded halfway .

Are they put on with machine screws from under, or is the threads there to stack them as I have observed in several catalogs?

There is a Small hole about 4 inches above the vin number tag .What is that used for? There is also a hole beneath and to the left of the tach coming thru the firewall.

How is the speedometer cable routed. When I had received the car the previous owner had taken a few liberty's with the tunnel area sheet metal.
Does the Speedometer go thru the tunnel somewhere, or thru the firewall.

Any help would be appreciated