What was the OHM and size of the 1961 Rear Speaker.
The master parts book says the rear speaker is same from 47-62 then changes from 63 on.
Neither the parts book or service manual actually say what the speaker size is.
I hope you say 6x9 10 OHM. But I think it is 8 OHM. And one place said it was a 5x7.
IMG_20231117_121636673.jpg
8 is the minimum in order for you not to fry your radio. They repop the speakers if you need one.
https://www.smelectrotech.com/
The older speakers and head unit used a common ground. I don't know all the ins and outs, but I don't think you can just use a modern speaker that matches the ohm rating. I am sure someone here will post more details about what is and isn't possible.
EDIT: After a little research, I think the issue is that you cannot used a modern radio with a common ground, so maybe speakers are ok.