Yep, the 2003 Viper is all new from the ground up. The wheelbase has been lenghtened (2 inches IIRC), but the overall length is about the same (1/4 longer IIRC).
The frame's torsional strength has been improved, the rear sub-frame has been substantially strengthened.
The overall weight is up by about 100 pounds.
The clam-shell hood is gone. The roof really keeps weather out now. The engine displacement increased, as well as horsepower.
All new suspension geometry front and rear. Bigger brakes, better clutch.
Not much of the car has been carried over from last year.