Ideally? I'd prefer to see a smarter V10 engine.
Something considerably lighter using high-tech materials.
As it stands, the main weight-sink in the Viper vs. most other cars "is" the engine.
DC needs to take a long, hard look at the LS-series of engines from GM. A lightweight, high horsepower output engine is the way to go. If you keep lumping displacement onto an engine, you reach a point of diminishing returns.
Also, a balance has to be reached if the car is ever to go racing. The old 8-liter engine was excellent for its original purpose. the 8.3 is pushing it. Anything bigger is practically un-needed. You want something reliable, but you don't want something that's heavily overbuilt for its purpose. Like I said, equilibrium.
Another thing, perhaps a 72-degree V10? It would certainly make the car sound considerably better. Ever heard a JUDD engine?