I went from the left-seat of the 1900 to the left-seat of an F-90 (single-pilot operation). Insurance approved me to fly the airplane right off the street, and the only requirment was completing an approved syllabus and simulator training within the next 12 months. If you can fly the 1900, you can fly any model King Air with ease. In fact, the F-90 with an AP, Avidyne EX-500, GNS-400W, Jepp. Chartview and NEXRAD was easier to fly single-pilot than the 1900 was with two of us up-front.