First off, ANY stock or correctly modified Pantera, if well maintained, can easily handle 5,000 miles per year.
Second, IMHO, when you say you don't know much about Panteras, I get a uneasy feeling in my gut.
These are a very easy car to buy incorrectly. If you do not learn how to properly inspect a Pantera, or have the help of someone so skilled to help you evaluate your potential purchase, well... I wish you luck.
PIM is a well known and respected vendor. That said, they are selling that car on consignment and their goal is a sale. Sort of like buying a house. Buyer beware. PIM will not lie to you, but they may not educate you as to any shortcomings the car may have, either.
From the description and photos it appears to be a substantially stock car save for the engine rebuild, radiator, Wilwoods (just calipers, or rotors, too?) wheels, and some appearance upgrades. What there is seems to be pretty common for the course.
You may find a suspension in need of all new bushings. Cooling tubes may need replacing, or not. All rubber hoses might need replacing, or not. And there may be rust.
At $60,000 it is over priced, IMHO. You should have some bargaining room; the seller has probably instructed PIM with a bottom price. PIM wants it to sell for as much as possible. They probably are not in a hurry as they do sell a large number of cars and they know this one will sell in due time.
There were about 150 USA GTS cars. They were nothing out of the ordinary mechanically, but had some appearance changes.
This car is lacking the original GTS steering wheel. It is lacking the original Campys and the GTS center emblems. It has an upgraded interior. Point being, any special 'value' it has as a GTS has been compromised.
Being in LA, you are surrounded by POCA chapters and owners. My advice to you would be to hook up with some of them and learn more before making your purchase. The POCA website has all the chapters listed.
Also, a GREAT opportunity awaits you this June 2-6 in Reno. The POCA Fun Rally, our annual gathering. Sort of like a crash course in learning about Panteras. Go to www.poca.com and find the details. Anyone can attend, you do not need to be a member, though I'd advise you to join.
People buying a Pantera often fall prey to The Fever. The cars are hypnotizing, and once you start looking at them, you want yours NOW. Relax, get to learn about the various flavors they come in, what can and should be done to them, and what shouldn't.
Adopt the attitude each day brings you closer to YOUR car. Generally, when you find it, it will speak to you. Sounds corny, but others know what I mean is often true.
Keep asking questions. That is the best thing to do before, and after, buying a Pantera.
Larry