The most desirable rims are the ones that are original to the bike. Fair Lady should have S7s with the stamps to the side. They take special diameter tires, noted by the fractional width marked on the tires as 1-3/4". Yes it sounds weird, diameter denoted by width, but trust me, that's how Schwinn did it.... surely so that you had to come back to them for tires.
S2 rims are typically associated with the rear wide Slik on the back of boys Stingrays. Their diameter is a more standard size, easier to find tires to fit, and marked in decimal sizes such as 2.125", and can fit as small as a 1.75" wide tire.