Keep a sharp look out for light weight lugged steel frames with cotterless cranks. Way back in the last century we used to do the "two finger" test. If you can place the two fingers of your right hand under the top tube in the bike's center of gravity and lift the bike off the ground without hurting your hand it's a very nice bike. Try it. Do it on an old Huffy. Then try it on a Centurion. You probably can't even get the Huffy off the ground.