Mate of mine just did an LS3 conversion on an early 3L GU. He did it himself.
Before he committed he asked me what it would cost and I told him $15k+ if he did it himself. He knew better and thought $7k tops, as he was doing it himself.
Last figure he told me was $16k and it still wasn't wired, tuned or close to running. It's running now and he loves it.
Anywho, his running 3L was still sitting in the corner of his workshop last time I was there. If it's still there, his wife would sell it for beer money, as it was 'blown up beyond repair,' hence the LS3 conversion.
Let me know if you want me to see if it's still there. Only a couple of hours from Kingaroy on the Sunshine Coast.
Shane.