[Ramairnacho]

I'm no expert but original speakers and radio are touchy. Meaning not upgrading radio to handle the second rear will break radio. The ohm going to second speaker will probably burn out original unit. I would have it digitized but having stock appearance with rca jack blue tooth ect. Tuck a small Amp for 6 x 9 s and have the speakers modernized too. I personally am trying to figure out if stock square speakers can be updated to modern more durable speaker material and better ohms. I had a 1973 4 speed formula with a nice Kenwood pull out, modern infinity 6 x 9 's in baffles and 2 free air 12 inch woofers behind the seat using trunk as speaker box. It sounded good but again wasn't stock. In my opinion stock sound quality probably isn't that good without doing some upgrading.