05 is the same as the rest of the late model Yammies. Hyvo chain. Top gears will swap, bottoms will not (not sure, didnt own a Viper)
Warriors were 23T top, 121 sleds are 24T. Any gearing will work, but you will need to clutch around it to get the results. Going down a tooth on a stock 121 sled will hurt it.
The stock clutching doesnt lug the motor no where enough as is, much less gearing it down.