Actually, the machines are wired the same and the only slight difference is the Vidiot deluxe. The pinouts and wiring between the machines are identical.
When I had my Granny, it had a Baby Pac ROMs on the MPU and the game worked, but not properly. I swapped in the proper ROMs and the game worked fine.
The only thing I ever really found different between the Granny and Baby was the theory of operation for a Vidiot Deluxe. Other than that, they are the same. (Of course, the wiring for the playfield is different).