there is tons of info on the net on all series of mustangs, suggest you get on your horse and start searching.
here's a starting point, spec sheets
price looks about right, if its in top shape, but i assume its not supercharged (too bad).
the saleen mustangs ran a 302 great engine, but most of the upgrades were bodykit and handling.
likely its safe to say most owners of these cars added a supercharger, as it really fits with saleen set up. if you ck the forums, do some searches you will see what other owners have done to their cars. get online with them and they'll be happy to share info.
the "fox" body mustangs were not generally very popular with mustang enthusiasts, but lately because of their relatively low price they have become more interesting to enthusiasts.
if your dad's fox body 87, is tight and has decent mileage with a little work and some modifications this will be a fine car.
Original MSRP: $20,999
Low Retail Average Retail Value High Retail
Base Price $5,325 $6,525 $8,750
Factory T-top Or Sunroof $250 $325 $450
TOTAL PRICE $5,575 $6,850 $9,200