Are 95 3000gt's reliable above 200k miles?

The transmission, sensors, and internal engine parts will be your main concern. With the mileage being so high anything could possibly fail at anytime, not trying to get your hopes up on the car but just going on what has been told isn't always the best idea, you never know what the car has been through or what has been done for maintenance purposes. Just prepare yourself. I would look into a rebuild or engine swap out. Look at it as a project car if you do decide to buy. These are not to complicated of a car, so I think it would be a great project for a future mechanic.