Just a note about ECU's. My Camaro(with an LT1) has a factory engine anti theft system, I believe it's called CAGS. If your car has it, the ECU reads the chip in the your ignition key. It looks for a set resistance (as burned into the computer) through the chip, if it doesn't match, the car will not start. I only mention this because you said you were going to replace the ECU. If you do replace the computer and your car has CAGS, get the chip out of the donor car ignition key and place it in your key.

Keith