If you want to use only one Synchronizer SPM-D2 to parallel to independent GCB's you can use 

the SPM-D2 PSY version providing 2 parameter sets (A and B). SPM-D is paralleling e.g. first breaker A (with Parameter Set A) , after breaker A is paralleled , the generator voltage is switched from Generator A to Generator B.  Parameter set B is activated by terminal DI 6 and now you can parallel breaker B having as well different breaker closing time then breaker A.

SPM-D PSY versions

8440-2170  SPM-D2-10B/PSY5-FU-D with 24VDC power supply

8440-2173 SPM-D2-10B/PSY5-FU-D-W with wide range power supply  90..250 VAC / 120…375 VDC

  Parameterset (B) can be activated by switching dicrete input 6