Looks great so far!
I assume you used nik's 03 Suburban as a base? You've got the correct 01-02 HD hood but those HDs also had a slightly taller grill and a thicker bumper filler. If you want, I've got a Duramax base I could send you if you need it.
I've got an 01 Silverado 2500HD 4x4 ECLB 8.1/ZF6
in my driveway at my shop, so I can get you reference pictures of just about anything you need besides the Duramax, Allison, and dually-specific parts.
I'll also try to remember to snap pictures of the GM 99-02 truck interiors at the local scrapyard next time I'm there.
Feel free to shoot me a PM anytime if you have any questions or want reference pictures.