You get an increase of 183 cc when you use the 1200 engine. Thats a step up from 988 cc to 1171 cc. [18.5% increase] It doesn't sound like a lot, but it's ALL in the stroke, from 59mm out to a whoping 70mm & that translates into more usefull torque. Auto transmissions love torque. From 61.5 ft-lbs out to 70 ft-lbs which is a 13.8% increase

The 1200 pedal box is NOT interchangeable with the 1000 one.