I was under the impression megasquirt is more commonly used in the UK? So you may find not as many are familiar with it here in Aus. But thats not to say don't use it, I'm sure there a few who have used it and runs fine.
What id recommend is talking to a few local tuners at they recommend. At the end of the day unless your comfortable doing all the tuning yourself, its them that needs to know what they're working with.
There are numerous ecu's that can do the job your asking. From relatively cheap to mega expensive.
Seems that Haltech has a strong following with local tuners, giving decent price and features.
Previous thread might help you to..
http://www.classic-ford.org/cfp/tm.aspx?m=32299