To move revenues, expenses etc. between classes we set up two "other income" accounts.  An intracompany contribution income and an intracompany contribution expense.  These will report below your ordinary income on the PL and should always net to zero, since it's just moving revenues, expenses, etc. between classes.

So your entry would be

dr.  intracompany contribution expense         Class 3

      cr.  overhead expense                               Class 3

dr  overhead expense              Class 1

     cr. intracompany contribution income          class 1