Hi there.
When you say "PAL mod" I assume you mean get the internal tuner changed. The answer is no. Many people do run their USA purchased TiVo with a digital set-top box like you wish.
If however you mean by "PAL mod" that you think the TiVo only does NTSC through the RCA connectors then this is true if it comes with a hard disk fitted loaded up with a USA operating system (image). For use in Australia you are going to ditch this image anyway and load up the Australian (OzTiVo) Guided Setup image which turns your TiVo into a fully PAL record and playback device.
So the short answer is to buy one. It will work with your tuner
Cheers
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