Here are the engine measurements:
1st set of pictures, paying specific attention to the forth (motor mount) picture:
http://www.discountscooterparts.com/E1000.htm
Now that we have determined a 150cc GY6 engine will fit in there, you have to measure your case length:
Long case (11.25 inches)
http://www.partsforscooters.com/150c...&category=8423
Short case (9.5 inches)
http://www.partsforscooters.com/150c...category=84231
(there is a shorter case, but it would be a buggy motor, and not suitable for a scooter)
And yes, it would be nice to put a 250cc engine in there, but it won't fit, and is water cooled.