After you run the Migration Assistant, restart your GibbsCAM.
Go to "File", "Machine Data".
Set Fixture Attachment Nodes to TG1 (Tool Group 1)
Set Fixture Type to "Any Type"
Put a check in the box under Toolblocks in the "Alberti Right Angle Heads"
Click "Save Changes"
You can then select the Right Angle Head.
See screenshot below.