what rear wheel are you going to use? If you have the original wheelset and it is 6/7 speed.. you might want to just use that.
If you are going to buy a 9 speed cassette, you are going to need a wheelset that is compatible with your cassette.

You are going to need a chain that is compatible with your cassette, cable housing, downtube cable stops(if you are going thumb shifter or barcon).

You going thumb shifter or downtube shifter??