Radio wiring diagram

Don't know 75 but in 67 there is a 12v in, a dash light in and 2 wires out to speaker, (single speaker AM radio) ground is thru chassis
Yea that sounds like mine it has a red going in and a orange going to the light and two black (with with green on it) going out the side. So both the in are hot! Here is my plan I gotta figure out how to ground it but I got a bluetooth board I'm gonna put in the radio I am gonna connect the hot to the original hot and ground it on the side somewhere take all the guts out and replace them with the bluetooth board. That way I can use all the original wiring and the radio will still looks stock.

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