Hi Gerardo,
if it is only about replacing the CPU I can send you an "old style" Rockwell or Ricoh which will do the job for the next years.
I have experience with WDC 14 CPU in Polgar and MM V and it works well, also with tuning at 10 MHz. In MM II there are problems with LED control. In SuMo and Monte Carlo it works well as replacement, but for tuning at 8 MHz you need to replace some ICs with faster versions for correct display function.
Some of the modifications necessary at WDC 14 are a little bit strange. Pin 8 (5V power) has to bend out of the socket and connected to Pin 36 which also has to be bent out. So, knowbody knows where 5V power comes from, but it works fine.
Cheers,
Andreas