More Electrical Help ...

OK. I think I am f&^%ed...I now have 24 VDC at the battery and the rest of the dash is dead. Not sure what I did (fried the ammeter?), but that's where I am now - how did I get 24 volts at the battery?? I am lost.
Lets step back and see if we can understand what is you have and what is going on.
If you can take a photo of the '62 engine and inteiror wiring diagrams from the FSM it will help us see what differences with '62.

Stock wiring?
Are there any electrical items added or alternations?
With what are you measuring the voltage? Could it be a setting on the meter? Scaling or zero function?

The ammeter is basically a big fat metal plate with a little parallel circuit which moves the needle to show discharge or charge. For example engine off, dome light on, you'll see a small amount of discharge on the needle.
High voltage alone shouldn't damage it. Excess current through it can melt things depending on how much current, for how long, and how that particular meter is constructed. If you see it pegged either direction - that's too much!