Mechanical Issues with high mileage mustangs?

You have the manual tranmission, which is a huge plus. An automatic wouldn't be likely to have made it to 190k miles anyway

It is mostly just normal maitence and common sense, like replacing the struts and shocks, making sure there's no excessive rust on the body or chassis, and keeping the brakes and other systems maintained. You'll have to inspect your car to see if it will be needing brakes, shockes, ect yourself. Tie rod ends are another thing to check, but at this point I bet it has seen new outer tie rod ends at least once.

These cars are really pretty cheap to repair and maintain, and actaully really easy to work on.

On my old '90, after 156k (80,000 of which were my miles), I had replaced:

Alternator
Starter (while chasing down alternator issue, probably didn't need done at the time but I did anyway)
Water pump
Wiper motor
Tie rod ends
one ball joint
clutch cable
exhaust

I think that's it, but I can't remember...

Your U-joints may need replaced before too long, I had to do the ones in my thunderbird last summer I think it was. Fairly easy job though.

run it till it blows and then get a 2.3t

I've got 192,000 on a '91 and there's only been a few things outside of regular maintenance that I've had to replace. Bear in mind that I did have to rebuild the engine when I got the car, but other than the crank and one rod, it was a ring and bearing job. The original pistons are still in the block and the original valvetrain is still in the head.

I still have the original A/C compressor converted to 134a
Since new it's had 2 alternators.
I just recently replaced the power steering pump and rack and pinion
As a preventative issue, I replaced all of the front suspension bushings and struts.
I just recently replaced the original water pump. and still have the original heater core and radiator.

Like anything, if you take care of it, it will take care of you.