Dear Don't under estimate your Mira 660CC. You have very best car and it is after all Japanese powerful machine, it is not pathetic local Mehran / Cultus / Sentro even Civic etc. I have Mitsubishi EKWegon 660CC and I visited Murrey last month ... It was hell much of enjoyment driving my automatic EK 660CC .... Although there is not any comparison b/w Murrey and Naran's Road but still you shouldn't have any problems till NARAN Insha ALLAH. After Kiwai and Kaghan there will be some road diversions due to land sliding where you should remain careful but these are not dangerous at all. If any car can cross these diversions, I assure you, your mira will be two steps ahead of these Insha ALLAH but please be careful.
Please take deep look into your machine before putting your foot into pedal towards Naran after BALAKOT. Car's battery should be OK, Air Pressure in tyres should be OK, all the plugs should be OK and most importantly your breaks should be OK. I know you know all these precautions but still we are human beings and in excitement we use to forget minor things. Just put your car into D2 gear and handle the steering and break and your car will take you to NARAN without any problem. Insha Allah ... I am also planning to go NARAN on my EKWegon in mid of june so I could enjoy Saiful Malook Lake, Jalkhad, Basel, Lulusar Lake and Babusar Taap.
I hope this will help you and will boost your confidence. Please share your experiences once you come back from safe trip.