And you can have stab tank on a 747-300.
From a Maintenance Engineering perspective a differences course between the 747 classic and the 747-400 is approx 8 weeks training. There are many many differences, and it would take a long long time to even attempt to go through them.
For instance the elevators on the classic are cross connected LH outer to RH inner but on the 400 they are connected LH outer to LH inner.