Mep 004A neutral / ground bond question

[charger53]

I have a MEP 004 that I converted to singe phase to provide backup power for my house / barn and whatever else. I have the electrician coming next week to install a 200 amp double throw transfer switch. My confusion is the correct location to remove the ground / neutral bond. Can anyone tell me the best place to disconnect it? The transfer switch does not transfer neutral.