Kernow Models has made some American and Fishbelly bogies available as spares: these were engineered for their steam motor model.
I bought a couple of the American bogies, and here’s a few notes on EM conversion:
I had to replace the existing wheelsets, I used Alan Gibson Mansell wheels.
The wheels would only fit if the electrical contact bearings were removed. I have no need for them, so out they came. I reamed the axle holes slightly, but did not fit bearings.
Brakes had to be pared back, and watch out for delicate components such as footsteps.
They work fine!