Yes, the 426 N6 engine can be slowed to l2 rpms. The pulley is already on the combine. (I am guessing you have an N6 motor you want to put in a l2) The N6 motor runs 220HP and the base l2 (301 engine) only had 130HP (not sure what HP 426 l2 had)You may be able to run it without doing any pump work. Still would be better to have pump shop adjust your fuel curve to factory,rather than 'de-tuned' N6 settings