Main Body is from the Raider

Main Chassis is made from a pair of Stun V1s

Rear seats are from the original Stun as are the side guns

Front missile rack and missles are from the Snow Wolf.

After a certain number of defeats Cobra Commander realized that his vehicles just couldn't stand up to the advanced armor of G.I. Joe. M.A.R.S was commissioned to create a larger, better armored fast attack vehicle for Cobra.

What they delivered in the Stun II is a vehicle that maintains the speed and fire power of its predecessor, while improving in armor, maneuverability, and stability at speeds. In initial designs the Motor Viper II and gunner were covered by an armored canopy, Cobra Commander had it scrapped for cost reasons. Since then it has been found that the removal of the canopy has also forced the Motor Viper IIs to drive in less predictable patterns.

From the G.I. Joe Command files:
The Stun II is a much more formidable weapon that the previous Stun. Combine that with the nut cases they give the controls to and Cobra has a very dangerous new weapon.