Thanks dear for your reply, as far as engine swap, I had discussed before engine swap and most of the geeks suggested to change it, its effect would be positive as mileage of my car was 244000 km at that time, and the cost of engine overhauld would have been equal to what I spent on swap.
CNG is installed on my ride and it give around 170km without AC and 130-140km with AC with 60L cylnder