The best way of synchronizing the multiple electrical circuits

clear your question please .you want to sync the gen sets or want to bring the electronics card on same bus?

If you mean Electrical Power circuits, to synchronize two or more circuits is to connect these circuits to a common bus after inssuring: (1) Matching phase sequence (2) Matching Frequencies (3) bring all circuits to same phase step (4) and matching the voltages- but you can allow some droop.