With the 6 bolt pattern and Viper wheels I'm thinking they put it on a Dakota frame....
Based on the engine setback, wheelbase, and the boxed rockers to clear the exhaust routing, I'm pretty sure it's actually a rebodied Gen 3 Viper.
After looking at the pics more, I think that you're right.
If they did that they stretched the Viper frame to get that wheelbase. A Vipers wheelbase is only 96 inches which is short compared to most cars. That looks longer than any Vipers stock wheelbase.
