I visited previous posts and All previous thread/suggestions are atleast 8 to 15 years old.
So for new comer like me really need this so that anyone requires information may get from this thread.
So criteria is
0. 660cc, 1000cc or 1300cc?
1. Fuel Economy ( atleast 17Km/L in city and 22 Km/L on long).
2. Auto Transmission if possible.
3. Easily availability of Engine in market and low maintenance cost.
4. Low swap cost.
5. Cost of engines, and other accessories requires for swap.
i have these points in mind you can add others if you have,