It depends. If you are rated on the 737-200 SP177 you can do an abreviated rating (3-4 days sim plus ground school) the SP177 has the 300 style dual autopilot and auto throttle etc. If however you are only rated on the SP77 (manual everything) then you can either upgrade to the 177 then the NG or do a full type rating. Both will give you 300-900. The problem is finding a suitable 737-200 sim.