Welcome to the forum. As this is your first Mustang you might try the FAQ section for some insite into what you got, what we are all about and what's available. For some info specific to your car, try www.martiauto.com
for a vehicle history report, reproduction window sticker and some other stastics. Kevin Marti bought the Ford Automobile assembly data base for cars 67 on up and can provide some data for a price (about $30 and up). As to rare, my records show 65,696 hardtops produced in 1971 out of 149,678 total Mustangs. It was not a good year for sales so there arn't many around. Figure that after 37 years on the road that half are gone and the remainder are probably not in the condition of yours. My personal advice, keep it stock, or at least make 'bolt-on' changes - starting with the air cleaner and a Pertronix ignition system. Oh, consider subscribing to Mustang Monthly magazine. They have a lot of good tips, articles and pictures. For pictures of you car, if you have them in a .jpg format in your computer, use the additional options to load them. Limit size to about 100k.
(And I like Kentucky Bourbon.)