The best thing to do is when you buy the motor get them to write you a reciept with the engine number, vin the engine came from if available, K's on the car if aplicable, then when you fit the engine to the vehicle go to a place that does blue slips and they fill out a blue slip with the new engine number on it then go to the rta with it tell them you have swaped a motor over and that you want it changed on the rego papers. Hope this helps you