and I need to get a new freewheel.. It's a '77 Trek TX770 and it's stock other than the Shimano 105 RD-5500 rear derailleur. Can I swap the freewheel for a 9-speed freewheel if I get a 9-speed chain? Will it work with friction shifters and the stock chainrings? Also, I'm unsure if 9-speed freewheels actually exist. I did a search on google shopping and some showed up, but I'm not sure if it's a freewheel or a cassette that got mislabeled. I've never heard of anything bigger than a 7 speed freewheel.