A quick search found these, don't know if they are still available or not....
http://dallas.craigslist.org/dal/pts/1838954238.html
out of a 2006 escalade suv..comes complete with wiring, cpu, and all assc., manifolds, trq. converter, intake to oil pan. 50k miles, $1650.
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http://dallas.craigslist.org/dal/pts/1819404580.html
$1000, 68K 6.0 out of a 2002 Trans Am
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http://dallas.craigslist.org/dal/pts/1816908238.html
$1600, 64k miles w/12 month warranty
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http://dallas.craigslist.org/dal/pts/1811966104.html
$1200, 6.0