Union Pacific 4-8-4 #809 re-fit

[trainable]

I was wondering if all of the models of the UP Overland 4-8-4 steam loco with the Vandy tender have interchangable bodies. I know that the chassis are not interchangable. The reason for this question, is that I have one with the split frame and 3 pole pancake motor that is built into the metal of the frame. Not the plastic housed one. Not sure if this is an older or newer version of the DC loco, but I want to keep the look of the loco and the tender. The jump starting of the pancake motor is a pain at the least, and undesirable to me. It seems to be either Mach1 or dead stop. Remotoring this chassis would require a lot of metal cutting and some sort of gearbox (maybe nwsl?) and I was thinking that if I could just pick up another chassis and motor and pop my existing boiler/cab cowcatcher onto it I would give it a try. I don't know if they are compatible. Any thoughts?
Roy