I was considering this swap myself into a E36 M3 a few years ago.
The LS6 is a simple, economical yet powerful engine that belies it's cost.
I routinely got 30mpg with that engine in my C5Z vette when it was stock, yet able to consistantly run mid 12's at the track with street tires.
If anyone else needs a source for LS based engines and T56 driveline parts, let me know. There's Champion Motors in Scarborough that is a premier Corvette tuner shop, and is a excellent source for used GM parts from Vettes.
I just swapped out my complete T56 driveline a few months ago and replaced it with the T6060 (from the ZR1). The T56 is more than enough up to 500HP, but beyond that, the T6060 driveline is designed to hold up to 800HP, and more refined.
Good work DANIMAL, and I'm certian she'll put a smile on your face every time, especially when any M3 believes your easy prey.