I'd say it ALL depends on the level of rust/filler on the car.
I'd price it as a 69 GTO project car with no engine, since basically the engine has no value unless it's used as a daily driver.
That said, if the rust is minimal, I've seen 69 project cars that complete (and by "complete" I mean no engine, no doors etc) sell for $10K. Again ... must have little to no rust/filler.
At 65 years old ... if I really wanted it, yeah, I'd pay $10K, if I was 50 years old I wouldn't think twice before buying it.
If it's the really "the last thing you need right now" ... my life advice would be to pass it up. Are all your other projects complete? Are all the things important to you in life sorted out? Will it make you feel better or worse seeing it sit outside neglected for a few years? Don't let that GTO hoarding animal get hold of you
If you want to buy it for $5K and flip it ... do it in a heartbeat. I bet you could get $8-10K for it pretty easy if it starts and runs.