For first timer on speedy who actually want a 'speedy' look, a common movement will do the job. Unless you are a collector. you opt for the 321 movement like what other sifus mentioned.
Sorry to pour cold water though, its not cheap to service a speedy. For a chrono, and if one of the gear mesh goes. an entire set of gears need to replace. (not only 1 wheel gear) I, myself find out the hard way.
dc