Mooky,
In NSW you can install a 138 red or 149 without upgrading to disc brakes or getting an engineer's certificate. CraigA's car has been modified in this way.
Note that as Simon said you'll still need to get the engine mounts on the cross-member to support the red motor.
You have to weigh up how you want to use the car with how original or authentic you want it to be. If it's a daily driver and you are going to go to the trouble of fitting a red, I would recommend getting discs as well. They're a bolt-on proposition (and you can keep your original king-pin x-member should you ever decide to revert the car back to original), and you won't know yourself in the stopping department! There is an article on our
Tech Info section about fitting a HR front end.
A grey crash-box will go OK behind a 149. Wouldn't recommend it behind a 186 though, unless you're very gentle on first gear!
Hope that's some help. I'm pretty sure the rules are the same in Queensland.
cheers
RET