I have seen one with 350k running a couple of years back, oh_my it was an 89 still the original motor(from what he said) he was selling it for like a grand, and it was probably worth it, but I got nervous by the mileage and mild smoke when floored. But it had a lot of pickup, and rust too.
As for how long can it last. Scott has 280K, thumbs_u keeps her maintained, use GTX10-30 every 3k, and do not let stuff slide(codes,noises, leaks) and you too can have 200 hp at the tires with 280K on it. But you have to maintain the car. If you do, she can last a good 250 and up, when the motor goes, swap it with another and go.
The SHO is like any car, take care of it as you beat it, and it will hold up to a certain degree, let stuff slide, and your FORD will be
Found On Road Dead
Fixed Or Repaired Daily oh_my
or Fixed On Race Day thumbs_u
Just my thoughts. Craig