It depends. If the radio is factory then you should have the factory style wiring in the door jambs and to the speakers with wrap and number tags (not some home made stuff)
Is the rear speaker in a metal frame with metal cover/grate? The rear speaker could be the dealer installed rear speaker kit used since the early 60's (available as a separate accessory) and was included in the earlier reverb dealer installed kit. Again it would have a wirign loom not indiviual wires. The fram would carry a Ford number. But most likely its just some PO adding speakers ;(
No there was no four speaker option in that year from the factory in these cars. Please understand that just a few years prior FM wasn't even stero.
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