Measure the space between the rear dropouts 120mm would mean it was 5 speed in back 126mm would let you run 6 speed both would have been a freewheel rear hub. If it's like my Mom's 80's Capri it would have been 27" steel rims. Now is the perfect time to upgrade to Aluminium wheels. I would look on craigs list, yard sales, etc for a donor bike or used wheels. I've picked up complete bikes with great donor parts for $30-40. Bring a magnet and buy rims that the magnet doesn't stick to.
Stuff like this you get the wheels and extra parts or sell the rest for $20.
http://milwaukee.craigslist.org/bik/3452282613.html
http://milwaukee.craigslist.org/bik/3507064335.html