the Stinger and the Yakuza Stinger are the same, and so is the convertible Stinger, but they are all very original. They look very much like the new Pontiac Solstice Club Racer, but that wasn't out when the game was made.
The ice cream van seems like it could be a Toyota Hiace with the ice cream van stuff, but at the same time, it just looks like any rounded cab-before-wheels van.