Slave solenoid vs Ford starter solenoid differences
 

What are the actual difference between the slave solenoid vs a Ford starter solenoid? I have to replace mine and I want to replace it with a ford solenoid because the local auto parts store carries them in stock vs having to get an overpriced one from west marine. both solenoids have copper battery terminals and bakelite bodies. Does anybody know what the ACTUAL differences are other than Sierra throwing a "Marine" name on the box. I know the mounting feet are a little different, but what about the internal guts?