From what I've read about MS is you either have to convert the whole ignition setup to something MS friendly or piggy back the stock ecu.
The easiest is MS for Fuel and the original controlling spark. I believe the OEM ecu can be retuned, so you could do that spark that way.
The reason its hard to do fuel and spark on the LS1 is that it uses a bunch of sensors for positioning instead of a simple CAS or decoder wheel, that and isn't it COP? I don't think MS supports that yet, just wasted spark.
Mario