You can make them all fit, some with less effort than others... just a matter of what your choice is for brands... do a search there is a lot of info for the best pipes for a viper
Yes, they say you dont have to put the opti-cool headgasket with those pipes, but if it was my sled, i would put one on for cooling down the cylinders. Hope you have the rear heat exchanger, good for a viper even without pipes! Good luck