[Plums]

You'll definitely need the IAT sensor, when it's not connected the PCM will see -39 degrees. There will be no timing reduction as temperature increases which will basically mean the thing should ping it's head off....

All 6 litre engines had MAFs, so depending on your engineer you may need to run with it.
Mike is quite correct about the LS1, HSV had a 300kW MAFless version in the earlier GTS's, though they did use a slightly different engine, the C4B. I would think that theoretically you should be able to say that you're running the HSV 300kW program and get away with it.