allanhurst:
That's pretty fancy LM317 to supply 30A...Where can buy one?
LM-317 (TO-220 case) drives 1 MJ2955 (PNP - TO-220 case) drives 4 2N3771 in parallel with 0.1 ohm, 16 watt emitter resistor (load balancing) on each 2N3771.
It's a very simple circuit and it has virtually perfect regulation (there is NO change in output voltage between 0 load and a 20 amp load).
The circuit even has remote sensing (which is why it regulates so well).
I can post the diagram of it for you if you're interested.