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.