The new quad isn't far off from being a rider. You could certainly get both of them in good running order.
That carb could work, but it's not likely to be original. Mine is identical to your black quad, and i think our friend's quad is the same as your multicoloured quad. BTW, Krylon Fusion is an excellent paint for plastic, in case you want to convert it from the pinto look.
Both mufflers look stock to me.