I don't have all the exact part numbers but there are two 960 motherboards. One says '960 Mother Board', and the other '960 Stepper/Video Mother Board'. The only real difference in them is a single polyfuse on the '960 Mother Board', 3 polyfuses on the '960 Stepper/Video Mother Board', and the 960 stepper only has 10 ohm resistors in all the SENET signal lines. The Stepper/Video does not. I've noticed that the 10 ohm resistors fail on the Stepper board when there is some kind of SENET problem or some idiot hot swaps the MPU or I/O cards.
That being said, I'm sure you can use the 960 Stepper/Video for both, but I'm not absolutely sure you can use the Stepper only backplane for 3902's. BTW... The connector spacing etc is the same. They are the same signal wise per pin. The BV connector is turned 180 degrees. Also the backplane EEPROM notch faces the other way.
FWIW, I use the older '960 Mother Board' in my test fixture for 3902's. Seems fine. '960 Stepper/Video' is part number 75905300. '960 Mother Board' is 75905700.
1270, and 044 motherboards are totally different. The MPU board connectors are spaced differently so you cannot plug the wrong MPU in.
There are at least 2 different 1270 backplanes. They seem to be interchangeable other than one of them has an additional security function I think is related to the Bill Validator. It causes some of the 6+ versions of 1270 MPU's to have a boot problem if the Varta is removed. I see this mostly on 12701 REV A MPU's. I have a secret fix. The motherboards both say 'MTHRBRD, S2000 Enhanced' I have part number 75909100 REV A in my test fixture, and two spares with the same number.
As far as I can tell, there is only one 044 backplane. I think it says Game King Enhanced MTHRBRD on it. Can't miss!