Do I need to replace a speaker? 1967 Dodge Dart 270

I would not waste my time buying and installing a new speaker until you have tested the radio and determined what the problem actually IS

Might be antenna, might be radio, might be bad speaker, might be "normal" for what you have.

And it also might be power, ie a bad connection at the fuse, etc.

Don't you have ANY vehicle with an AM radio? When turned on and up, and between stations, they should produce a fair amount of noise and static, especially if near buildings / power lines etc.

You can test the antenna to "some degree". Unplug it, and bring the connector out. Check resistance from the center pin to the outside of the connector. Should be open, IE infinite. Clip an alligator to the antenna proper. Check resistance to a body ground "for good measure." Again, open. Now with one meter lead clipped to the antenna proper, touch the other lead to the connector center pin. Should be a dead short, IE continuity

You can "rig" a speaker, surely you have a computer speaker lying around? -----to the speaker connections at the radio. Sounds like you do not have a factory fader / rear speaker, but you might want to make sure.

No idea what you have for local stations. Here we only have one in town, it comes in "loud." The Spokamentro stations vary according to location and conditions.