[alffie]

Ive had no problems with my LS7 and E38 ECU, cost $A440 to have it tuned for the cobra and mafless tune added 50 more HP! GM make the engine harness complete and the body computer plugs in to the ECU harness. Holden dont they have the body harness plug in to the engine aswell as the engine harness. The GM harness are cheap and simple everything plugs into the ECU and you will only have a few plugs out of the ECU for gauges etc.
Why dont you get an LSX 427? They dont have the dry sump and you can run what ever crank you want.
The Tremecs are about the only choices you have. Id go for the T56 with the 31 spline main shaft out of the viper. around $A5000 brand new.