I think that nautilus machine pullovers have no alternative or substitute. Barbell/dumbbell pullovers have a completely different range of motion and target the muscles of the back from a completely different angle. I would incorporate both in my workouts on and off.

I TRAIN AT HOME SO NO PULLOVER MACHINE.TRY STRAIGHT ARM PULLDOWWNS ON A LAT MACHINE SUPERSET WITH DEADLIFTS OR BARBELL ROW.SINCE USING THIS METHOD MY BACK IS NOW WIDER AND THICKER.I SUGGEST THIS TO ANYONE FOR THE PUMP IS AMASING WHICH I NEVER USED TO GET IN THE BACK WHEN TRAINING IT BEFORE.