Performance of ford mustang with 100,000 miles?

The performance of the vehicle should be the same unless the car was abused & hotrodded and not taken care of. You should get at least another 100k if you take care the car and keep it garaged or stored when not in use. In terms of appearance some 1999 model Mustang GT's had a rare black honeycomb taillight panel that was really cool. The only other noteworthy Mustang appearance packages was the 2001 Bullitt Mustang and the 2004 Mach-1 Mustang both will be highly sought after as collectors items in the next 10-15 years.