These appear not to be add-on wiring but do appear to be factory speaker wiring.
I'm not that familiar with 74's but the color codes and stripes cause me to think that they are. I'm assuming I'm looking at the rear shelf. The only other wiring near there would be for the window defroster... and would be just one pair.
Along those lines, many years ago I re-registered my car at the local DMV and the sweet young lady inputting my data turned and said... "BTW, do you know what the rear window defroster on a FIAT is for?"
I kinda stammered and said, "Well, its for defrosting the rear window like any other car."
And she says, "Yes, but its primary purpose is so you don't freeze your fingers while pushing the car..."
HAHA! Everyone has gotta get their digs in!