There are a couple of different Seamaster Chronos, the blue classic with a 6-9-12 A7750 and a black 3-6-9 model. Personally I would suggest that you have the movement serviced. If you have the blue model, you can put a gen ETA 7750 in it as well. Putting a new A7750 in it would be your cheapest option, but you are back to having an unserviced movement, and your results may vary.