First let me address the question about gauge size. The gauges I installed were 3 3/8", and it looks like a 4" gauge would fit perfectly. Oh, well live and learn, and now someone gets to learn form this if you try and improve on the idea.

4" circle for fitment test.

Dash Lights and gauge lights on. I like how this turned out.
sorry for the fuzzy picture
And now for the drum roll, today the motor came to life. Man these LS3's are cool technology. Unfortuanatly the cold air intake routing is not complete so the microphone pics of more from this giant sucking sound of air that any exhaust note, but once this is buttoned up this huge air pump is gonna put some HP to the pavement. The Z06 cam sounds mild now, but can't wait to hear the roar when I take it for a spin. Since she started up now it's time to finish up the interior re-install.
Nothing like the nervous energy from a first time startup, and then she comes to life.
What a great day!!!!