Mighty Dave Mac!
Martin's Engine Reconditioning comes highly recommended: 86 Gipps Street Wollongong, phone 02 - 42299899 and ask for Bernie. I know it's out of the Sydney metro area, but they do quality work, according to my engine builder. They do block cleaning, decking and can install hardened valve seats for unleaded. In my engine 3.8L Holden V6 valves were used instead of the red motor ones (machined to fit of course).
My engine builder told me that porting a grey motor head is about 20 hours of work. So that can be a bit of money, depending on whom you get to do it.