Yea sorry bro, that's not really a conversion... That would be lotsss of work.
However if your dead set on it, look into the city jetta. The rear tails are somewhat similar to a mk5, at least the top portion of them. The bottom portion of the tails you could shape and cut them to be more mk5, and then custom the quarters and trunk to fill in the space of the tails you shape/cut. Hope that made sense lol.
Either way it would be a **** ton of work and not worth it in my opinion. But good luck :thumbup::beer: