Not sure if there is an absolute way, but one easy clue would be to pull the console and see if the floor pans have the threaded riv-nuts installed. Should be 2 of them, one about center of console and the other towards the rear of the console. Could even crawl under the car with a light and have a look. Anyone adding a console I would seriously doubt they would go through the trouble to install riv-nuts.
As far as the wire harness goes. It might depend on whether the console is equipped with gauges or not? Gauge consoles have a large bundle of wires where as a non gauge console may only have 1 or 2 wires for lighting (don't remember if they have a rear dome light in a non gauge console)
Mine is a factory gauge console car but the wire harness had been cut on and things removed so I couldn't tell you for sure about the harness deal. One thing I did notice on mine and it's also in the assembly manual, is that the factory harness that comes down to the console runs along side the heater box and there is a rubber coated metal "J" style holder just for holding the console harness before it disappears under the carpet.
Something brought to my attention recently is that factory console cars had 2 piece front carpet from what they had been documenting here (as mine does). But original carpet would have to be present obviously. Haven't heard mention of one piece front carpet on console cars but that doesn't mean anything either.