mopar radio questions

I have a stack of mopar radios that I need to test. These units are all AM units from 68-69 Mopars.

So what I would do is connect the radio to my replacement speaker, hook up an original factory antenna, and use my power supply to provide 12vdc to the power wire. Does this seem ok? Does the radio take 12v or is the voltage reduced to something else before it gets to the radio?

Second question; I am having the antenna hole welded up where it comes thru the fender. Does anyone make an aftermarket antenna that can be mounted under the dash or somewhere else on the car? Thanks much.