If your wheel hasn't been lacquered, then most aluminum polishes will do the trick. Just remember to put a good coat of wax on it or you'll be doing again real soon. The wheels aren't too hard to come by, but the hubs are getting tough to find. Besides the obvious aesthetic appeal, the smaller diameter make life a little easy for big/tall/large driver.
BBAY
'63 300SL
'85 500SL