Tip to insulate wheel contacts from loco frame:
I repowered an old Manuta 060. The wheel power pickup was mounted to the frame with a rubber bushing around a 1-72 screw. Bushing fell apart.
Stuck with no replacement part, I tried a 1/8"L piece of shrink tubing on the screw (loose, not shrunk). As I tightened the screw, the tubing compressed under the head and formed a perfect bushing.
Terry