So much depends on condition that it's hard to say with any certainty. Auto on the column makes it a very rare optioned car, and that's low mileage for a 69. If it's otherwise in good condition, this sounds like one that I'd vote for going %100 original on - that would preserve the most value. What's the seller asking for it?
When you go look, take plenty of photos and post them here. Examine very closely for any hint of rust in these areas:
* Bottom of front fenders between the door and wheel opening - below the GTO emblems and above/behind the trim
* Base of windshield
* Rocker panels (bottom edge under doors)
* Bottom edges of quarter panels
* Around rear wheel openings
* Passenger compartment and trunk floor
Also check out the front bumper for nicks, gouges, and how well it fits to the fenders
If you can, get the codes off the engine (2 characters on passenger side front of block, just below head, 7 digit casting number on passenger side rear of block, down low, just 'above' transmission), and cylinder head codes (usually 2 large characters/digits "raised" on the center two exhaust ports)
If it really is 'numbers matching' you should find a string of numbers down low on the front of the block, just above the oil pan and next to the timing cover on the passenger side, that match the vehicle VIN number.