I also race in Australia.
The way you adjust armature timing is by holding the stacks and turning the comm clockwise (I think) when looking down from the top. You will most likely have to do this with a pair of pliers with a rag or something rapped around them to stop damaging the comm. I don't know what Paul thinks about it but I wouldn't recommend doing this to any armature other than a Parma chinese 16D. With all the different armature timings you can buy in most cases it isn't neccessary. Depending on what kind of motor it is you will find that sometimes the endbell is adjustable (Parma rotor and SpeedFX) or you can buy an endbell with a different hole patten which can advance the timing. This is most common in alumnium endbells for I-15, G27 and G7 but is also used for plastic endbells in G12.
The motor in your Top Fuel drag car would be a Group 20. I don't know a lot about drag cars but I know this is a pretty common motor for them. It is no longer used in circuit racing but in comparison it would be a bit slower than a Group 12 motor.