The only announcement I ever saw was in an old Bobbie Hall catalog of future Hallmark brass engines from the 1970s. If this would have been anything like their brass diesels it would have been pretty crude by today’s standards. With the 3D technologies and firms like Shapeways it’s possible someone might do one but I don’t know what we’d do for a underframe, trucks and power. I think 670 only ran initially between Union and Lincoln, Nebraska where it connected with the Missouri River Eagle and then was assigned to the Delta Eagle route so prototypically one is pretty limited but that’s never stopped us model railroad types has it? 
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