Thank you for the in depth response.These cars are very reliable and many parts are very durable however the car is 32+ years old. So things like ball joints, tie rods, sway bar bushings, struts... would be old, tired and possibly worn depending on maintenance and the way the car was driven.
My main concern would be the head gasket, they are not an issue on these cars but over the years I have seen many people buy F2T's that are still running very old, heat cycled, dried out factory head gaskets, they push the car harder than it's ever been driven, modify it, increase the boost and the head gasket goes and warps the head...
Also it has very low millage which is good for the most part but if the car sat for long periods of time and was used for occasional short runs to the store it can lead to oil baking into the piston rings and drying out the oil pump and rear main seal for the crank.
If your just looking for a daily driver, you drive like the elderly and all your purchase options are 30+ years old the 89mx6 would probably be more reliable than your other choices but if you plan on pushing the car harder than it's ever been you could end up finding and chasing the driest oldest rubber gaskets and seals one after the other..
Ideally if you replace all the engine gaskets, head and intake gaskets, injector o rings, valve seals, the small coolant hose between the intake runners to the idle valve, clean the piston rings, change the belts, new t-stat, rad cap, ATF, axle seals, exhaust manifold studs and gaskets. You will have a hassle free engine and drive train for many years to come.
I know it sounds ridiculous but if hypothetically the water pump starts leaking and the engine starts to over heat, you have the car toed to a garage and they do the water pump and timing belt, the extra heat affected the old head gasket and it fails a month later, the car gets toed to the garage again. Now your disappointed with your purchase, spent more on two repairs than having done everything to begin with and still have many 30 year old gaskets and seals on the engine.
Everything else is general maintenance and wear and tear.
Or the car could be perfectly maintained, spent it's life in the right climate and still have many reliable worry free years in it.
The potential concerns listed above apply to any 30+ year old car but because the MX6 GT is turbo charged and boost is addictive, a forced induction engine makes more power than it's naturally aspirated version therefore generates more heat, more pressure, more strain on everything and weak points can be found quicker.
Personally I think you should buy it.