I'm not sure where the carpet and insulation came from yet. When I bought the car, it was included with it, but it is the correct style for my deluxe interior.
As with the rear defroster, I have a knob on the side of the console that I've never seen in any car before, on the driver's side. I think that operates the rear window defroster.
I've installed carpet on numerous cars, and yes, I know to keep extra and slowly trim it. What's neat about the Vettes is the console and back seat carpet already covers the seams, mostly. I have a feeling it's already easier than, say, my 69 Chevelle was, or even my 83 GT Mustang.
If I remember right, the back carpeting, which is in great shape, has grease markings below that too. For now, I'm thinking about just keeping it there and worry about the floors.
As for the rear gears, I'm pretty sure I have 3.08s. Done the math and it's right on.