All that really matters is price. Salvaged title cars (any car, not just Vipers) have an obviously lower resale value.
A car is just a car....they can all be repaired as long as the damage isn't too extensive (in Ontario there are some wrecks that are stamped "Unrepairable"). Go over the car with a fine-toothed comb and try to source your parts before buying the car so as to keep the financial surprises to a minimum.
If it's cheap enough and you can finish it for a decent price then go for it.
The value of the car is subjective to potential buyers. A younger, less financially stable person looking for a Viper will probably jump at the idea of owning a Viper for an affordable price so long as the car checks out under inspection. Similarly, someone looking to build a race car will also rather have the money saved than be concerned with titles.
My '94 cost me 37K Cdn fully rebuilt by a professional. At the time a similar car in excellent condition was worth 65K. I wasn't concerned with a few scratches as long as the frame was properly repaired and the drivetrain was ok. It was the only Viper I could afford at the time.
I drove that car for 4 years and sold it for 2K more than it cost me.
Figure at least a 30-40% reduction from retail value if it has a salvage title. Mine didn't, which made it an even better deal, although by law I still had to make potential buyers aware of the fact that I had rebuilt it. Some buyers were understandably scared away, but many simply did their due diligence on the car and decided from there.
Bottom line being, if you can afford one that hasn't been hit, obviously that's the way to go. If you can't, and your heart is set on owning a Viper (like mine was at the time) then just make sure that you get a good enough deal to justify the sacrifice down the road when it's time to sell it.
I'm actually looking at a hit '04 SRT with 75 miles on it right now.