Referring to the brochures, I believe the 250 version is called the "Chopper." And as far as size of engine goes, it depends on the year. My brochures start at 2005 and it was 117 cu. in. through 2011. Not sure if larger options were available as they are now in the present. Let me post a few pics from brochures and hopefully that will answer your statistical questions regarding dimensions. Give me about 15 minutes.
Actually, it is not the "Chopper" Model. They came out with the K9 250 in 2011. 2011 Big Dog K9 250 2011 Big Dog K9 250
MSRP $22,595
The Big Dog K9 250 is an all new chopper that is cheaper than the original K9 but did not hold back on the chopper either. It has a 1807cc displacement and a 6-speed direct drive.