My brother has a '94 Mustang and they are heavier (read slower) than the 87-93 style and they also have a different style of computer that isn't as racer friendly as the 87-93 style. So he does recommend staying away from the 94'-95 style.
Getting one that someone has already started is a good idea, because of the front struts, rear suspension pieces, gears, and other items. When you do pick a car, look to try and get one that already has the 5 lug wheels. They can be converted with wheel bearings and rotors, but that is an added expense.
Bill M