Hi Havago,
Welcome, fellow Aussie here, QLDer also

... having just been through the compliance for my B2 which was a complete rebuild here's my 2 cents. If you haven't converted to RH drive yet, I wouldn't unless you've really got your heart set on it. Here's why I think that:
1. With the import rules the way the are in Australia (and about to change again) it's getting harder to find these cars in general in Australia, and especially in good condition.
2. You potentially lessen the resale value of the car.
3. Compliance/Modification plates are a pain in the a** to get to start with, without adding fuel to the fire by swapping left to right
4. I'm not entirely sure if you can get a RH drive firewall for a 69/70 Mustang. You might be able to...if not obviously it's going to have to be custom.
Having said that, I totally get why you would want to swap it. It's your $$$$ /time and effort, so if you are going to do it you'll have to research a lot before you start swapping it, especially re compliance (and this goes for anything else you want like brakes or even if you have to have yellow rear lights on tail for indicators). There's an awful lot of misleading/conflicting information out there re this in QLD. One person told me I needed to tell the transport department what camshaft I'd installed (BS!!!

).. (they wouldn't even know what the cam numbers meant!

)
Don't know anything about power steering install, looked at it briefly but decided against because we didn't want to collapse the steering column.
Cheers
HB.