Stewart John Regan aka Nano the Magician/The Magician (people close to him were always disappearing). He was involved with the loose coalition of crims, the so called Toe-Cutters Gang, and one himself (that is, a criminal who preyed on other criminals). He was also involved in prostitution and organised theft rackets. I believe he also had some involvement in real-estate (obviously on the dodgy side ).
Even though James Linus Driscoll aka The Pom was convicted of the Jake Mahoney murder, several sources cite Regan as his true killer. I think it was '74 he died. He was a true nut-bag and hard man, like most of the figures involved in the scene around that time.
That's really about it, off the top of my head. I must apologise, I'm typing on a new computer and still waiting for old hard-drives to arrive, and unpacking all my books. I'd recommend the Gangland Australia series and Shotgun and Standover, both co-written by James Morton, for some more insight into the Sydney scene in the '70's.
If you are still interested, I can post more when I can access all my old shit.