Did he get the FAA certificate "based on" the other license (a 61.75 cert) or is it "stand alone?" If it's a 61.75 cert he can have the 707 added on at the private level. Then if he gets a stand alone certificate the type can be moved over.
However if he already holds a stand alone certificate he can't back track to a 61.75. The only way to add the type would be to complete a ground school and checkride.
Is Travolta hiring?