While Dean's suggestion of paralleling regulators should work, I have never seen it used in any power supply I've came across.
They all had a stack of parallel transistors, driven by a single regulator to increase the regulator's current capacity.
Maybe its just too hard to get multiple regulators to share the current without upsetting one another.
The stack of parallel transistors all have an individual series resistor (~0.1Ohm/ 5-10W) at the output to make sure the slightly different transistor ratings are balanced out.
I have a 10-15V/ 40Amp power supply here that uses a single regulator driving 6 bypass transistors, all on a fan cooled, mighty big, heat sink.