[dfariswheel]

Those are real Colt grips, but not for the Viper.

These were a later rubber grip Colt used for the flat black finish models of the Cobra and the Commando Special version of the Detective Special made during the big Colt strike.

The Viper was only produced in 1977 and those Colt rubber grips were only made in the mid to late-1980's.
The Viper used a grip that looked like the wood "Combat" grips Colt used on the later Detective Special and Cobra, only the Viper grip was longer on the bottom.
Viper grips turn up from time to time on Ebay, but the sellers usually think they're DS grips.

Here's a set of later Colt Combat grips. The Viper grips look the same only longer: