Sounds like a good start

Don't forget the 6 x Emitter ballast resistors (each should drop 100mV
at full load), so maybe 10 milli ohms each (short length of electric
heater element ?).

May need a fan to keep the heatsink cool.

You probably also need to mount the driver transistor on a heatsink.

Regulation using an LM723 or similar. There should be plenty of
detailed designs out there - also see the Nat Semi application notes on
the subject.

See http://www.national.com/pf/LM/LM723.html

Regards,

Mark.