I’m scratchbuilding a gas mechanical railcar similar to the MAC 4-40 (see this month’s NGSL Gazette) in 1:20.3. I need some ideas on how to power it. Ideally I would use a motor/gearhead that would fit under the hood and a differential on the front axle. I’d like to keep the cab free for a speaker. I’d like the unit to have enough power to pull one or two 30-foot cars, as the prototype did.