Stags were unquestionably the archetypal bad BL car when new - they were shoddily built in every way. Panel fit was poor, paint finish was muddy, and worst of all, the engines were famously unreliable.
This last was what killed the car at the time. Owners and enthusiasts have since established what the problems were. The alloy heads / iron block combination gave rise to electrolytic corrosion in the waterways. The water pump is mounted above the engine, so if you lose even a small amount of water, it stops going through the pump and doesn't circulate. The capacity of even a well-sorted factory-fit cooling system is marginal for a car of this size.
All this can be fixed. You need a 50:50 anti-freeze : water mix all year round, not just in winter. You have to pay attention to the water level not just in the expansion bottle, but also in the radiator itself. The later high-pressure cooling system, and perhaps and auxiliary fan, can then cope with even very hot days.
And then you're sorted.
Stags don't really rust. Well, they do, but in an honest way; aside from the sills, they don't rust in places you can't get at. If you can't see rust on a Stag, then chances are, there isn't any.
The engine noise is just awesome. It's somewhere between a rumble and a rasp which just gets better as the car picks up speed. There may only be 146bhp there, but there's 170 lbs/ft of torque, so the car can really pull.
Handling is so-so. The wheelbase is long, and with rear-wheel drive, the back end tends to want to overtake the front. It is perfectly adequate for posing purposes.
The ride is smooth and comfortable. You can drive 300 miles in a Stag and get out not feeling tired. The only issue perhaps is the noise level - with the roof up, this is a noisy car at speed, between engine, road, and slipstream noise. Be prepared to invest in a good loud stereo.
Technically it has 4 seats, but in reality adults get uncomfortable in the back after about half an hour. It is perhaps a 3-seater, or a 2+2.
Stag owners tend to keep their cars a long time. The reason becomes obvious when you drive one.
I will never sell mine, except as a p/x for a really good Jaguar XK140 DHC.