Replacement motor for 2nd Gen 4-8-4

[fuchst]

I have old 4-8-4 Daylight, not the pancake motor but not the newest style.  The engine runs great but will not climb a 2% grade with more than 2 cars.  I have several newer style 4-8-4s but would like to modify this to a GS2 engine rather than just discard it.  Has anyone used another non-Bachmann motor in one of these engines?  I am not opposed to doing some modification to the frame. This model has a rather large flywheel with the gearing on the outside of the flywheel.  Seems like this would be gearing the engine pretty tall.  If you have modified one of these I would be interested, or.... are there any tricks to improving the torque of these older motors so modifying the frame would not be necessary?  Steve, near Walla Walla