Come On Guys, Let's Go An AB6 had an E6B carbody modified with a single 1000 h.p. engine, windows and controls at one end, baggage compartment, and steam generator. Only two were built by EMD in June 1940 for the Rock Island (#s 750 and 751) for the Rocky Mountain Rocket (Google it). The train would run from Chicago to Limon, CO with an EA-unit on the front and an AB6 second. The train was split at Limon with the AB6 taking a few cars to Colorado Springs and the other unit taking the rest of the cars to Denver. The reverse happened on the trip back to Chicago. The EA6s lived out their lives in commuter service in Northeastern, Illinois. A second diesel engine was added in the baggage compartment making each a full E-unit.